Vaccine prioritization: Canadian Pandemic Influenza Preparedness: Planning Guidance for the Health Sector

Pandemic Vaccine Prioritization Framework

Table of Contents

1.0 Introduction

Annex D: Preparing for the Pandemic Vaccine Response to the Canadian Pandemic Influenza Plan for the Health Sector (CPIP) 2006Footnote 1, provides detail about the pandemic vaccination program in Canada, including considerations associated with prioritization of a pandemic vaccine and their implications for planners. The Annex emphasizes that prioritization decisions (if required) will need to be based, in part, on data that will not be available until the pandemic virus has started circulating. The Pandemic Vaccine Prioritization Framework has been developed as guidance for those who will be making the recommendations on whether or not priority groups are required and, if they are, on who will be members of those groups. Note that this prioritization process does not address the larger question of the opportunity costs of using pandemic vaccine with other measures, including those for seasonal influenza. That question is part of a risk assessment process that is distinct from the prioritization process for recipients of vaccine.

2.0 Other Examples of Vaccine Prioritization Frameworks

Prioritization strategies for pandemic influenza vaccine in other countries have been reviewed in several recent publications.Footnote 2 Footnote 3 Straetemans et al.Footnote 3 looked at 27 countries of the European Union and the Global Health Security Action Group. The authors found general agreement among the countries reviewed on the make-up of several priority groups – health care workers (100% of countries), essential service providers (92%) and high risk individuals (92%); however, the rationales for the choices were not always included in country plans or, if included, the rationales were not always comprehensive. Only one-third of the countries reported consulting ethical experts to guide vaccine prioritization decisions. The discussion in this paper emphasizes the importance of clarifying the goals of prioritization and proposes the inclusion of ethics experts and the results of modelling exercises to help guide the decision-making process.

The United States provides the best examples of comprehensive prioritization processes, both at the state level (for example CaliforniaFootnote 4 and MinnesotaFootnote 5) and at the national level.Footnote 6Footnote 7 These American approaches include several commonalities:

  • a multidisciplinary work process;
  • consideration of a wide range of factors beyond science;
  • identification of a range of potential vaccination goals and strategies;
  • consideration of pandemic epidemiology and vaccine characteristics;
  • consideration/development of ethical values and principles;
  • consideration of societal values;
  • public and stakeholder input and consultation;
  • a complex ranking and scoring system to integrate various factors and create prioritization lists;
  • emphasis on a fair and open process.

The US federal guidance on allocating pandemic influenza vaccine identifies vaccination target groups for pandemics of varying severity, using a tiered approach to prioritization.Footnote 7 In contrast the Minnesota recommendations encompass an ethical framework of principles, goals and strategies to guide the pandemic vaccine prioritization process and include a sample rationing plan to illustrate the framework’s application.Footnote 5 While the Minnesota framework is closest to the framework proposed in this document, there are lessons from all of the American approaches that are applicable in the Canadian setting.

Another pertinent approach is provided in the analytical framework for vaccination programs in Canada known as the Erickson De Wals framework,Footnote 8 which is familiar to program planners in Canada. It was developed to assist in the analysis and comparison of potential immunization programs, for example, by national immunization committees (e.g. the National Committee on Immunization and the Canadian Immunization Committee) and their provincial counterparts, but has also been used in a variety of different contexts. The framework includes 58 criteria classified into 13 categories, which are addressed through a series of questions. The criteria and categories used in the Erickson De Wals framework are comprehensive and similar to other pandemic prioritization frameworks that have been reviewed. Thus it provides a valuable framework that can be readily adapted to the purpose of prioritization of individuals for receipt of a vaccine in short supply.

3.0 Proposed Pandemic Vaccine Prioritization Framework

The proposed pandemic vaccine prioritization framework (see Table 1) consists of a series of criteria organized into categories, with key questions identified for each of the criteria. It is adapted primarily from the Erickson De Wals frameworkFootnote 8 but has grouped the criteria and categories to make them more manageable. The key questions have been adapted for a pandemic vaccine prioritization scenario. Two criteria from the Erickson De Wals framework have not been included: cost-effectiveness, because the CPIP indicates that vaccine will be offered to all Canadians; and ability to evaluate, because this will not guide initial prioritization choices, although it is acknowledged that evaluation may affect course corrections.

Table 1 – Framework for Pandemic Vaccine Prioritization
Category Criteria Key Questions
1. Scientific evidence a. Disease characteristics and burden How severe is the pandemic?
Who is most affected in terms of illness, complications and death?
Who are the persons most likely to spread infection?
b. Vaccine characteristics Are there any expected population differences in protection from the pandemic vaccine?
Are there any persons who do not need the vaccine?
Is there a need for a second dose? Can a reasonable degree of protection be achieved by a single dose?
Are dose-sparing strategies possible, e.g. intradermal administration?
Are there any vaccine safety concerns?
What is the proposed indication for use and what indication/market authorization has been granted by the Health Canada regulator? What pre-market assessment has been performed, and what post-market surveillance requirements are imposed?
2. Ethical considerations Ethical considerations What ethical principles and values should be applied?
How do they inform the decision?
Are the recommendations fair and equitable?
3. Program issues a. Vaccination strategies What strategies might be considered?
Do the proposed strategies support the pandemic goals, and how?
Are there important knowledge gaps that affect choice of strategies, and can these be addressed through timely research?
What is the timing of anticipated vaccine availability in relation to pandemic activity?
What other factors might affect the strategies (e.g. antiviral use, development of antiviral resistance)?
b. Logistics What is the rate of vaccine production, release and delivery?
What is the size and anticipated vaccine uptake of each potential priority group? Is the target population accessible?
c. Program acceptability What are the public and stakeholder values that can inform decisions about vaccine prioritization?
Should there be any alterations because of public or provider perceptions of disease severity or risk of vaccine?
4. Additional policy considerations a. Legal considerations Are there any applicable legal considerations?
b. Conformity of programs What are other countries doing?
What degree of provincial/territorial variation is acceptable?
c. Political considerations Will the proposed prioritization plan be free of controversy, within Canada and in an international context?

4.0 Considerations in Applying the Pandemic Vaccine Prioritization Framework

The Canadian pandemic goals provide strong direction to the choices to be made in implementing the pandemic vaccination program. These goals are set out in the CPIP:

First to minimize serious illness and overall deaths, and second to minimize societal disruption among Canadians as a result of an influenza pandemic.

PATHOGEN SAFETY DATA SHEET- INFECTIOUS SUBSTANCES

SECTION I - INFECTIOUS AGENT

NAME: Eastern equine encephalitis (EEEV), Western equine encephalitis (WEEV)

SYNONYM OR CROSS REFERENCE: Alphaviruses, sleeping sickness, encephalitis, EEE, WEE, equine or western equine encephalomyelitisFootnote 1-3.

CHARACTERISTICS: EEEV and WEEV belong to the genus Alphavirus within the family TogaviradaeFootnote 1. They are 65-70 nm in diameter, small, spherical, and enveloped viruses with an icosahedral symmetry and triangulation number of 4Footnote 1Footnote 4. Their genome is comprised of a single stranded positive sense ssRNA of 11.5 kbFootnote 1. They replicate in the cytoplasm, with budding from the plasma membraneFootnote 4.

SECTION II - HAZARD IDENTIFICATION

PATHOGENICITY/TOXICITY: Eastern equine encephalitis (EEE) is the most severe of the arboviral encephalitides and has a mortality of 50 to 75 %Footnote 5. Symptoms of the disease include fever, headache, vomiting, respiratory symptoms, leucocytosis, dizziness, decreasing level of consciousness, tremors, seizures, and focal neurological signsFootnote 3Footnote 5. Death can occur within 3 to 5 days of infectionFootnote 5. Those who survive suffer from neurological sequel, including convulsions, paralysis, and mental retardationFootnote 5. Brain edema, ischemia, and hypoperfusion are present in early stages of the diseaseFootnote 3. WEEV causes asymptomatic or mild infections in humans, with non-specific symptoms such as sudden onset of fever, headache, nausea, vomiting, anorexia, and malaiseFootnote 3 . Some patients may also present with altered mental status and weakness, with signs of meningeal irritationFootnote 3. In rare cases, WEEV infection may cause encephalitis or encephalomyelitis, resulting in neck stiffness, confusion, visual disturbances, photophobia, tonic-clonic seizures, somnolence, coma, and deathFootnote 2Footnote 3. Fifteen to fifty percent of the encephalitis survivors, especially young children, suffer from permanent neurological damage (mental retardation, emotional instability, and spastic paresis)Footnote 2Footnote 3. Western equine encephalitis virus has mortality range of 3-7 %Footnote 3.

EPIDEMIOLOGY: EEEV is widely distributed throughout North, Central, and South America; the Caribbean; coastal region of eastern Canada; Poland; former USSR; Thailand; Philippines; andthe former CzechoslovakiaFootnote 2Footnote 5. In the United States, human infections due to EEEV are usually sporadic, with small outbreaks occurring each summer, mostly along the Atlantic and Gulf coastsFootnote 5 . Furthermore, the Centers for Disease Control and Prevention reported that 220 confirmed human cases of EEE occurred in the U.S. between the years 1964 to 2004Footnote 3. In Canada, infections due EEEV occur mainly in spring and are associated with birds migrating from southern United States to northern CanadaFootnote 2. WEEV virus is widely distributed along North and South America, but is absent from Central AmericaFootnote 2. The Centers for Disease Control and Prevention reported that 639 confirmed human cases of WEE occurred in the U.S. between the years 1964 to 2004Footnote 3. Children greater than 14 years of age have a higher chance of acquiring WEEV infectionFootnote 3.

HOST RANGE: Humans, reptiles, bats, pheasants, wild birds, mosquitoes, horses, dogs, and rodentsFootnote 2Footnote 3.

INFECTIOUS DOSE: Unknown.

MODE OF TRANSMISSION: The primary EEEV and WEEV transmission cycle occurs between birds and mosquitoes (Culiseta melanura for EEEV and Culex tarsalis for WEEV)Footnote 2Footnote 3. Both viruses are transmitted naturally to humans from bites of arthropods (such as Aedes , Coquillettidia , and Culex spps. for EEEV; and Ochlerotatus melanimon , and Aedes dorsalis for WEEV) which feed on both birds and humansFootnote 2Footnote 3.

INCUBATION PERIOD: The incubation period exceeds 1 week for EEEV (range of 4-10 days)Footnote 3Footnote 5. The incubation period for WEEV is 2-7 daysFootnote 3.

COMMUNICABILITY: Person-to-person transmission has not been reported for EEEV or WEEV viruses. Direct bird-to-human infection can occur although humans and horses are not amplifying hosts as virus titers in their bodies are insufficient to infect mosquitoesFootnote 2. Eggs of mosquitoes can be infected by the femaleFootnote 6.

SECTION III - DISSEMINATION

RESERVOIR: Wild birds are the main reservoir for transmission of both EEEV and WEEV virusFootnote 2. Humans, horses, and other animals (domestic fowl, feral pigs, cattle and rodents) are not significant reservoir hostsFootnote 2. Amphibians and reptiles are a possible reservoir for the virus to overwinter. Mosquitoes and infected eggs are also a reservoir for the virusesFootnote 6.

ZOONOSIS: YesFootnote 2. The virus can be transmitted from birds to humans via mosquitoesFootnote 2.

VECTOR: Both viruses can be transmitted from pheasants to humans by insect vectors, usually, mosquitoesFootnote 7. Aedes sollicitans , Aedes vexans , Coquillettidia , and Culex spps are vectors responsible for transmission of EEEV from birds to humansFootnote 23). Ochlerotatus melanimon (California), Aedes dorsalis (Utah and New Mexico), and Aedes campestris (New Mexico) are responsible for transmission of WEEV to humansFootnote 3.

SECTION IV: STABILITY AND VIABILITY

DRUG SUSCEPTIBILITY/RESISTANCE: None.

SUSCEPTIBILITY TO DISINFECTANTS: EEEV can be inactivated by exposure to 50% ethanol at concentration for 60 minutesFootnote 8. Most enveloped viruses are also susceptible to 1% sodium hypochlorite, 2% glutaraldehyde, quaternary ammonium compounds, and phenolicsFootnote 9Footnote 10.

PHYSICAL INACTIVATION: Microbial inactivation is possible using moist and dry heatFootnote 11. EEEV can be inactivated by UV raysFootnote 12.

SURVIVAL OUTSIDE HOST: Unknown.

SECTION V- FIRST AID / MEDICAL

SURVEILLANCE: Monitor for symptoms. Both EEEV and WEEV infection can be diagnosed using serological assays such as ELISA to detect IgM antibodies in serum and CSFFootnote 2Footnote 3. The viruses can be isolated from clinical specimens on Vero cells (African Green Monkey kidney cells)Footnote 3. Molecular biology methods such as reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR can also be used to detect WEEV/EEEV-specific RNA in clinical specimensFootnote 2Footnote 3. Virus can also be detected in clinical specimens or tissues with direct IFAFootnote 2.

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID TREATMENT: Currently no treatment is available for EEEV or WEEV infectionsFootnote 2Footnote 5. Symptomatic treatment is given to maintain vital functions of the bodyFootnote 2. Passive and active physiotherapy is used during the recovery phaseFootnote 2.

IMMUNIZATION: None currently availableFootnote 13.

PROPHYLAXIS: None.

SECTION VI - LABORATORY HAZARD

LABORATORY ACQUIRED INFECTIONS: Four laboratory-acquired cases of EEEV and sixteen cases of WEEV (with 4 deaths) have been reportedFootnote 14Footnote 15.

SOURCES / SPECIMENS: Infected wild birds; infected mosquitoes; infected pheasants; clinical samples such as blood, CSF, central nervous systems, other tissuesFootnote 2Footnote 3Footnote 14.

PRIMARY HAZARDS: Accidental parenteral inoculation, contact of the virus with broken skin or mucous membranes, and bites from infected laboratory arthropods or rodents are the primary hazards associated while working with these virusesFootnote 14. Exposure to infectious aerosols may also be a potential hazardFootnote 14.

SPECIAL HAZARDS: Infection of newly hatched chickens is hazardousFootnote 15.

SECTION VII - EXPOSURE CONTROLS / PERSONAL PROTECTION

RISK GROUP CLASSIFICATION: Risk Group 3Footnote 16.

CONTAINMENT REQUIREMENTS: Containment Level 3 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.

PROTECTIVE CLOTHING: Personnel entering the laboratory should remove street clothing and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashesFootnote 17.

OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) or other appropriate primary containment device in combination with personal protective equipment. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are loaded or unloaded in a biological safety cabinet. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activitiesFootnote 17.

SECTION VIII - HANDLING AND STORAGE

SPILLS: Allow aerosols to settle, then, wearing protective clothing, gently cover the spill with absorbent paper towel and apply appropriate disinfectant starting at the perimeter and working towards the center. Allow sufficient contact time before starting the clean upFootnote 17.

DISPOSAL: All wastes should be decontaminated before disposal either by steam sterilization, incineration or chemical disinfectionFootnote 17.

STORAGE: The infectious agent should be stored in a sealed and identified containerFootnote 17.

SECTION IX - REGULATORY AND OTHER INFORMATION

REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: October 2010

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada

Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright © Public Health Agency of Canada, 2010 Canada

REFERENCES:

Footnotes

Footnote 1

Jose, J., Snyder, J. E., & Kuhn, R. (2009). A structural and functional perspective of alphavirus replication and assembly. Future Microbiology, 4 (7), 837-856.

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Footnote 2

Krauss, H., Weber, A., Appel, M., Enders, B., Isenberg, H. D., Schiefer, H. G., Slenczka, W., Graevenitz, A. V., & Zahner, H. (2003). Viral Zoonoses: Zoonoses caused by Alphaviruses. Zoonoses: Infectious diseases tranmissible from animals to humans (3rd ed., pp. 6-24). Washington, D.C.: ASM press.

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Footnote 3

Zacks, M. A., & Paessler, S. (2010). Encephalitic alphaviruses. Veterinary Microbiology, 140 (3-4), 281-286.

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Footnote 4

Dimmock, N. J., Easton, A. J., & Leppard, K. N. (2007). Appendixes: survey of virus properties. Introduction to modern virology (6th ed., pp. 444-479). Malden, MA: Blackwell publishing.

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Footnote 5

Petersen, L. R., & Gubler, D. J. (2003). Infection: Viruses: Alphaviruses. In D. A. Warrel, T. M. Cox, J. D. Firth & E. J. Benz (Eds.), Oxford Text Book of Medicine (4th ed., pp. 377- 379). Oxford, New York: Oxford University Press. Retrieved from online.statref.com/Document/Document.aspx?FxId=94&DocId=1&SessionId=121DA8BAMRVOHFWX

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Footnote 6

Pfeffer, M., & Dobler, G. (2010). Emergence of zoonotic arboviruses by animal trade and migration. Parasites & Vectors, 3 (1), 35. doi:10.1186/1756-3305-3-35

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Footnote 7

Kalluri, S., Gilruth, P., Rogers, D., & Szczur, M. (2007). Surveillance of arthropod vector- borne infectious diseases using remote sensing techniques: A review. PLoS Pathogens, 3(10), 1361-1371.

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Footnote 8

Ali, Y., Dolan, M. J., Fendler, E. J., & Larson, E. L. (2001). Alcohols. In S. S. Block (Ed.), Disinfection, Sterlization, and Preservation (5th ed., pp. 229-240, 253). Philadephia, PA: Lippincott Williams & Wilkins.

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Footnote 9

Prince, H. N., & Prince, D. L. (2001). Principles of viral control and transmission. In S. S. Block (Ed.), Disinfection, sterilization and preservation (5th ed., pp. 543-571). Philadelphia, PA: Lippincott Williams & Wilkins.

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Footnote 10

Collins, C.H., and Kennedy, D.A. (1999). Decontamination. . Laboratory-Acquired Infections: History, Incidence, Causes and Prevention. (4th ed., pp. 160-186, 170-176). London, UK.: Buttersworth.

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Footnote 11

Joslyn, L. J. (2001). Sterilization by Heat. In S. S. Block (Ed.), Disinfection, Sterilization, and Preservation (5th ed., pp. 695). Philadelphia: Lippincott Williams & Wilkins.

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Footnote 12

Aguilar, P. V., Paessler, S., Carrara, A. S., Baron, S., Poast, J., Wang, E., Moncayo, A. C., Anishchenko, M., Watts, D., Tesh, R. B., & Weaver, S. C. (2005). Variation in interferon sensitivity and induction among strains of eastern equine encephalitis virus. Journal of Virology, 79 (17), 11300-11310. doi:10.1128/JVI.79.17.11300-11310.2005

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Footnote 13

Steele, K. E., & Twenhafel, N. A. (2010). REVIEW PAPER: pathology of animal models of alphavirus encephalitis. Veterinary Pathology, 47 (5), 790-805. doi:10.1177/0300985810372508

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Footnote 14

Agents Summary: Arboviruses and related zoonotic viruses. (1999). In J. Y. Richmond, & R. W. Mckinney (Eds.), Biosafety in microbiological and biomedical laboratories (4th ed., pp. 183-199). Washington: CDC & NIH.

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Footnote 15

Fleming, D., & Hunt, D. (2006). Biological safety: principles and practices (4th ed.). Washington: ASM press.

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Footnote 16

Human pathogens and toxins act. S.C. 2009, c. 24, Second Session, Fortieth Parliament, 57- 58 Elizabeth II, 2009. (2009).

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Footnote 17

Public Health Agency of Canada. (2004). In Best M., Graham M. L., Leitner R., Ouellette M. and Ugwu K. (Eds.), Laboratory Biosafety Guidelines (3rd ed.). Canada: Public Health Agency of Canada.

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How best to achieve the goals, however, is not clear-cut, as pandemic vaccine could be used in a variety of ways, as discussed in the following sections.

Using the framework to develop a specific pandemic vaccine prioritization plan involves consideration of the evidence related to each of the criteria and the applicable key questions in Table 1, in turn, followed by integration of the results as they apply to potential target groups. A formal weighting system for the criteria is not proposed at this time because it is felt this would be an artificial product that could not be defended. The epidemiological picture (disease characteristics) probably represents the most important consideration in the prioritization discussions. It is expected that the group developing the recommendations will provide a full rationale and identify the factors that weighed heavily in its decisions.

Developing recommendations for prioritization may not be straightforward. Not all of the necessary information is or will be available. Integrating age-based targets (which might be suggested by pandemic epidemiology) with risks from underlying health conditions and with occupational priorities could be challenging.

Potential data and information needs for each of the criteria are outlined in Appendix 1. Some of these data will be available only through special studies, for which protocols and arrangements should be set up in advance. Some measures, such as mortality measures, are open to a number of equally valid interpretations, as described in Section 4.1 below. Consideration of ethical principles and values, and an understanding of public and stakeholder values will help when alternative choices must be weighed.

The following sections highlight the data gaps and some of the potential pitfalls surrounding considerations of the criteria.

4.1 Disease Characteristics and Burden (Pandemic Epidemiology)

There are several key “burden of disease” measures for decision-making about vaccine prioritization, including pandemic severity, attack rate, and the groups most affected in terms of mortality and severe morbidity. Knowledge of the epidemiology of the pandemic and its disease burden is probably the most important consideration in developing vaccine recommendations, including prioritization of recipients.

Mortality data can be expressed in different ways, e.g. as the number or rate of deaths by age or risk group, or as years of life lost (YLL), which can be further refined into years of healthy life lost or working years of life lost. The choice of one of these mortality measures implies an ethical value judgement as to whether some lives (e.g. young persons or elders) are more important than others. YLL is supported by the observation that, in a pandemic, mortality is shifted to younger ages and by the likelihood of reduced vaccine response in seniorsFootnote 9 While there has been ethical debate (though limited) in the published literature on the general basis of age-based prioritization for pandemic influenza vaccine,Footnote 10-12 at this point it is not known which approach to reducing mortality is most acceptable to Canadians.

Burden of disease must also include a consideration of severe morbidity, which can similarly be assessed in different ways (e.g. disability-adjusted life years, long-term versus short-term sequelae, short-term impact on health resources).

Another factor in vaccine prioritization is whether persons who are most likely to spread disease should be given priority in order to reduce the risk to others. Traditionally, one would consider the risk that infected health care workers could pose to their vulnerable patients and the role of children in transmitting influenza within families and the community at large.

While the ideal would be to use Canadian data on disease characteristics, decision-making cannot be delayed if they are not available. It is hoped that detailed epidemiological data will emerge rapidly from the areas first affected by the pandemic. When available, Canadian data can be used to validate or adjust the plan.

4.2 Vaccine Characteristics

The pandemic vaccine is likely to differ from seasonal influenza vaccine in a number of ways (e.g. formulation, side effect profile, number of doses needed) that could affect a pandemic vaccination program. In order to stimulate immunogenicity in a naïve population, the pandemic vaccine may contain an adjuvant or may be a whole-cell product, which could increase the occurrence of local or systemic vaccine reactions. Given the urgency of pandemic vaccine production, the vaccine may be authorized for sale with limited safety data and minimal clinical effectiveness data to guide prioritization recommendations. Because vaccine will be given to large numbers of people within a short time frame, rare side effects may be detected and may affect the risk/benefit ratio in general or for particular groups of recipients as the program unfolds.

It will be important to determine whether there is a need for a second dose for some or for all potential vaccine recipients. If a second dose is needed, its timing needs to be addressed. The question for prioritization is whether to give everyone the first dose before starting second doses, or whether to begin second doses at the minimum effective interval, thus potentially delaying a first dose in some recipients. Optimal individual protection would call for the second dose to be given as soon as indicated (e.g. 3-4 weeks) after the first dose. If vaccine supplies are particularly tight and a single dose is shown to protect against severe outcomes, like death, greater community protection might result from giving one dose to everyone (conferring at least partial protection) before beginning the second dose, as suggested by some modeling.Footnote 13 However, it is possible that the first dose of vaccine will confer little to no protection in some targeted groups, highlighting the need for “real-time” data collection during the pandemic, as well as a plan for mid-term correction in roll-out strategies.

4.3 Ethical Considerations

The World Health Organization (WHO) has emphasized the need to strive for equity among countries for pandemic vaccines. Industrialized countries will have access to most of the world’s supply through their advance purchase agreements. In addition, national regulatory decisions (made primarily in the industrialized countries including Canada) can potentially affect other countries and could reduce the global availability of vaccine. Knowing that our decisions have an impact on others, it is important to keep the global picture in mind when decisions are made on the use of pandemic vaccine in Canada.

WHO has recently published guidance on ethical considerations in developing a response to pandemic influenza.Footnote 14 Chapter 3 of the WHO guidelines deals with priority-setting and equitable access to therapeutic and prophylactic measures. The key process recommendations include a way for setting priorities and promoting equitable access that involves society and relevant stakeholders and incorporates pre-established mechanisms for revising decisions, and for timely and accurate information to be provided to the public.

WHO identifies the following key principles that need to be taken into account in developing criteria for use in prioritization:

  • utility (the principle of acting to maximize aggregate welfare) - whether for individual or community benefit;
  • equity (the fair distribution of benefits and burdens) - this principle may sometimes conflict with utility considerations;
  • age – e.g. the “fair innings” argument (the idea that everyone is entitled to some “normal” span of life years). WHO notes that opinions were mixed on this criterion and that age-based prioritization criteria should be adopted only after wide public consultation;
  • non-discrimination against individuals based on inappropriate characteristics;
  • the goals of the vaccination program (noting that possible goals may compete with each other).

More and more jurisdictions (e.g. Australia, New Zealand, UK, USA) have developed an ethical framework to assist their pandemic planning.Footnote 15-18 Similarly, the CPIP contains a section called Ethics and Pandemic Planning, which identifies the ethical principles that have been used in national planning.

A number of Canadian provinces have adopted the ethical framework for pandemic planning prepared by the University of Toronto Joint Centre for Bioethics.Footnote 19 Footnote 20 The ethical principles and values identified in this framework and in the CPIP are summarized in Appendix 2, along with comments about their applicability to vaccine prioritization at a time of shortage. Quebec has also developed comprehensive ethical advice for pandemic planning.Footnote 21

Numerous relevant ethical debates are found in the literatureFootnote 10-12 Footnote 22-30 A full analysis of the ethical issues surrounding the vaccine prioritization question is beyond the scope of this document, but issues related to the principles of equity and their application to prioritization decisions must be highlighted. Both the WHO and the CPIP identify equity as an important ethical principle informing pandemic planning. However, there are other ethics principles that also need to be brought to bear, such as utility and optimizing the risk/benefit ratio. Further Canadian dialogue and debate on which principles should prevail under which circumstances would help inform decisions about the prioritization of scarce resources, such as a limited supply of pandemic vaccine.

4.4 Vaccination Strategies

4.4.1 Pandemic Goals and Strategies

As outlined earlier, pandemic vaccine could be used in a variety of ways (sometimes competing) to achieve the pandemic response goals.Footnote 10Footnote 22 Footnote 31 For example, to minimize serious illness and overall deaths one could concentrate first on those most likely to get sick or die, and/or one could vaccinate health care workers to maintain the functioning of the health care system and maximize everyone’s chance of optimal health care. Societal disruption is most likely to occur in a moderate to severe pandemic as a result of high absenteeism of the workforce. Vaccination of first responders (police, fire, ambulance) and other essential workers could minimize the additional impact of the loss of these services. Many authors present arguments to make children a high priority.Footnote 32 Footnote 33 Modeling of the impact of different strategies would be valuable and may be available from the Canadian or WHO pandemic modeling networks.

The stated objectives of the pandemic vaccination program in the CPIP do not provide further insight as to which groups might be vaccinated before others to achieve the overall pandemic response goals. These pandemic vaccine objectives are as follows:

  • provide a safe and effective vaccine program to all Canadians as quickly as possible;
  • allocate, distribute and administer vaccine as rapidly as possible to the appropriate groups of people;
  • monitor the safety and effectiveness of vaccination programs.

It would be useful to develop more specific vaccination strategies to address the pandemic goals. Once the most relevant strategies have been determined, identification of potential vaccine recipient groups is an easier process. (See Appendix 3 for a chart that outlines a range of potential vaccination strategies to address the pandemic goals and potential target groups for each strategy. Note that health care workers and high-risk persons are identified as priority groups in several potential strategies.)

The timing of anticipated vaccine availability may also affect the strategies. Availability between waves may favour prioritization of occupational groups in preparation for the second wave or those in high-transmission settings, such as school children, in an effort to flatten the epidemic curve of the second wave. Vaccine availability at the start of the second wave may lead to prioritizing the individuals who are at high risk of severe disease and complications, especially if immunity is expected to have developed in a significant proportion of other groups during the first wave.

Vaccination strategies also need to take into account the other planned interventions, especially the use of antiviral drugs or convalescent plasma. For example, the development of drug resistance, severe drug shortages or the unavailability of antiviral prophylaxis for health care or other critical infrastructure workers might affect prioritization.

4.4.2 Population Sub-groups

Annex D identifies a series of population sub-groups to be considered for prioritization in a prioritization plan. These population sub-groups are classified into high-risk groups, occupation-based groups, and healthy adults and children. The proposed population sub-groups from Annex D are set out in Table 2, but they will be refined at the time of the pandemic as an early step in the prioritization process.

Table 2 –Proposed Population Sub-Groups for Vaccine Prioritization (from Annex D of the CPIP)
Category Population Sub-Group Working Definition
*Might include existing high-risk groups as defined by the National Advisory Committee on Immunization: persons with underlying chronic disease, residents of long-term care homes, persons aged 65+, healthy children aged 6-23 months and pregnant women.
High risk (of poor outcome)   Groups in which epidemiological evidence indicates increased risk of poor outcome.Table 1 - Footnote 1 *
Occupational Health care workers Persons who work in settings where essential health care is provided.
Public health responders Persons essential to the public health response.
Key health decision-makers Persons whose decision-making authority is necessary for implementing and maintaining the health response.
Pandemic societal responders Persons who are trained or primarily involved in the provision of an essential service that, if not sustained at a minimum level, would threaten public health, safety or security.
Key societal decision-makers Persons whose decision-making authority will be necessary, at the time of the pandemic, to minimize societal disruption.
Healthy children and adults Healthy children Individuals 2-17 years of age who do not have a high-risk medical condition.
Healthy adults Individuals, 18 years of age and older, who do not have a medical condition or fit into an age category that would make them high risk and who do not fall into an occupation-based priority group.

 

Identifying persons and groups at high risk of poor outcome will depend on epidemiological analysis of who is most likely to develop complications, require hospitalization or die as a result of infection with the pandemic virus. The existing NACI recommendations identify high risk groups for seasonal influenza (see footnote to Table 2) based on age and underlying medical conditions. It is likely that these same conditions will also place persons at high risk during a pandemic. It is also possible that certain age groups will be found to be at higher risk during the pandemic or, conversely, relatively spared. For example, if an H2 pandemic were to occur, persons born before 1968 who were exposed to circulating H2 viruses between 1957 and 1968 might have some pre-existing immunity.

Review of pandemic epidemiology may also identify additional persons or groups at high risk of poor outcome due to additional chronic disease or risk conditions (e.g. obesity, asthma), or other factors such as gender, racial and/or ethnic status, socioeconomic status, geography (e.g. remote and isolated communities), and lack of access to health care. Vulnerable populations or special settings (e.g. correctional facilities) may be identified as potential targets.

Depending on pandemic epidemiology, vaccine availability and other logistical considerations it may be useful to amend the proposed population sub-groups. For example one might want to

  • divide the adult and child populations into narrower age bands to reflect pandemic epidemiology or pre-existing immunity;
  • expand and/or prioritize within the high-risk category;
  • identify settings to consider for prioritization;
  • prioritize within the health care worker or societal worker categories;
  • work on a more comprehensive list of definitions and inclusions in each category so that groups like the military and vaccine manufacturers are not overlooked;
  • consider “critical infrastructure” definitions when developing categories of societal workers and essential services. This approach is being adopted by emergency planners (see Appendix 4).

The lack of clarity in how sub-groups are defined (e.g. who is a critical infrastructure worker) has hindered efforts, especially at the provincial and territorial (P/T) level, to develop solid estimates of numbers in some potential recipient groups. The concept of including the person doing the task (who could be a volunteer or family member), not just the person with the job title, needs emphasis in occupational settings.

4.5 Logistical Issues

The current pandemic contract calls for Canada to have priority access to at least 8 million doses of monovalent vaccine (containing15 μg of antigen) per month over a 4-month period. GlaxoSmithKline's manufacturing capacity for pandemic vaccine has now exceeded the minimum specified in the contract, although actual production capacity may vary depending on a number of factors specific to the vaccine being produced. These include yield (amount of antigen that can be grown per egg used in production) and the amount of virus antigen per dose that is needed to immunize. Provinces and territories have indicated that they will be able to administer vaccine through local public health agencies as fast as it is produced, even if that were to involve providing one dose to the entire population within a month.

It is important to maximize use of vaccine; therefore, in addition to estimates of target group size, estimates of the anticipated uptake within target groups are relevant in matching up quantities of vaccine available to potential recipients. There are several additional options to consider:

  • whether more than one group should be targeted at the same time (the Americans are deliberately including at least one group from each category in each round of vaccination);
  • whether vaccinators can move ahead to the next target group if they have vaccine remaining;
  • flexibility needed for remote communities where it is more efficient (and probably more effective) to vaccinate everyone at the same time. Some remote communities lack ready access to medical services, so prevention of illness by early vaccination is particularly important;
  • consideration of holdbacks for possible redistribution if any lots have to be withdrawn or if a particular part of the country experiences heavier or earlier illness or has much higher vaccine uptake than other provinces.

The way in which vaccine will be allocated to provinces and territories is intertwined with prioritization, as it could affect the quantities available for general distribution. Beyond a general recommendation that P/T allocation be on a per capita basis, detailed discussions have not yet taken place on the actual P/T process.

4.6 Program Acceptability

Some of the specific concerns about program acceptability by public and stakeholders include the following:

  • unease or even mistrust of vaccines by some persons;
  • general acceptability of the priority choices (tied to public perceptions about mortality and value of life);
  • placement of children on the priority list;
  • perceived risk or benefit to receiving vaccine first;
  • use of a vaccine with limited safety and minimal clinical effectiveness data (may be reflected in the consent process);
  • public response to reports of severe adverse vaccine events;
  • vaccine uptake in a pandemic that is perceived as mild.

Although the CPIP is a public document and has included a vaccination priority list in previous versions of Annex D, there has been little public reaction to this list, except for some questioning of the low prioritization of children.

The TGAP (Task Group on Antivirals for Prophylaxis) deliberative dialogue processFootnote 1 explored public and stakeholder beliefs and values in relation to antiviral prophylaxis. The key values emphasized for decision-making were practicality, fairness and equity, compassion for the vulnerable, public awareness and engagement, and government leadership. These results are relevant to vaccine prioritization decision-making (see Appendix 5).

The University of Toronto Joint Centre for Bioethics, through its Canadian Program of Research Ethics in a Pandemic, is currently engaged in pandemic research projects that include stakeholder forums and public consultation about ethical values related to pandemic issues. This should provide helpful guidance when completed.

4.7 Legal Considerations

There are many factors that must be carefully considered in the development and use of a pandemic prioritization framework. If governments choose to create priority groups for the prioritization of a pandemic vaccine, they could face Charter of Rights and Freedoms challenges under section 15 (equality rights) and/or under section 7 (life, liberty and security of the person). It is important for governments that decide to create priority groups, therefore, to retain evidence that the decision to create the lists was based on a sound scientific, social, economic and ethical policy rationale. Governments should be able to demonstrate that the composition of the lists was based on reasonable, fair and rational considerations. Further, the policy decision to create priority lists should be communicated widely in a clear and consistent manner, and the prioritization framework should be followed carefully and precisely unless necessary modifications due to new evidence justify a change.

5.0 Using the Pandemic Vaccine Prioritization Framework

In Annex D, the Pandemic Vaccine Working Group is identified as having the responsibility for making recommendations for vaccine prioritization. The degree to which prioritization will be necessary will be linked primarily to the rate of vaccine production, which will not be known until production is under way. Provinces and territories have indicated that their capacity to administer vaccine will not be a limiting factor.

There is at present no prescribed specific process for applying the framework. There has been considerable P/T experience with the Erickson De Wals framework using a number of scoring systems tailored to specific circumstances. Such a formal approach, however, may not be necessary or practical in the circumstances, e.g. if the pandemic epidemiology differs little from the usual pattern of seasonal influenza where priorities for vaccination have already been established. In that case the framework would function more as a checklist to ensure that all relevant factors have been considered. It is anticipated that the group developing the recommendations will decide on the most appropriate way to use the framework and that it will provide a rationale for the recommendations and identify the factors that weighed heavily in the decision.

The appendices to this document provide several tools, such as a list of the data and information needs that should be assembled for the Working Group’s consideration (Appendix 1), and a draft discussion tool to assist individuals in assimilating and weighing the information (Appendix 6).

Appendix 1 – Data and Information Needs for Vaccine Prioritization Decision-Making

Here is a list of the data and information that will be needed for the prioritization process. This should be gathered, analysed and presented in advance to the group that will be doing the prioritization, to give them the opportunity to identify any additional analyses or information needed for decision-making.

1. Scientific Information

  • Pandemic epidemiology
    • Attack rate (age-specific if known)
    • Case fatality rate (age-specific)
    • Indicators of disease severity, e.g. rates of complications and hospitalization
    • Risk factors for severe illness, hospitalization and death
    • Population susceptibility – age-specific serosurvey data to ascertain pre-existing population immunity
    • Results of studies to address correlation of disease history with immunity
  • Vaccine information
    • Vaccine immunogenicity information by age
    • Vaccine safety data (clinical trials)

2. Ethical Considerations

  • Ethical principles from WHO and CPIP
  • Ethical frameworks (from Canada or elsewhere as appropriate)
  • Results of public consultations

3. Program Issues

  • Vaccination strategies
    • Summary of evidence base and modeling of different strategies
    • Identification of potential options
  • Logistics
    • Size of Canadian and provincial/territorial populations by age and sex (5 year breakdowns)
    • Size of all proposed sub-population groups and categories within them
    • Rate of vaccine production, approval and delivery
    • Anticipated uptake for subpopulation groups
  • Acceptability
    • Results of public and stakeholder consultations, media scan and opinion surveys

4. Additional Policy Considerations

  • Vaccination plans from other countries, especially the USA
  • Identification of other potential significant issues with policy analysis and legal opinion as needed (including liability issues)

Appendix 2

Relevant Ethical Principles to Consider
Ethical principle (CPIP 2006) Applicability to vaccine prioritization strategy
*Source : Thompson AK, Faith K, Gibson JL, Upshur REG. Pandemic influenza preparedness: an ethical framework to guide decision-making. BMC Medical Ethics 2006;7:12.
Protect and promote the public’s health Underlying premise of vaccination program
(but there are various strategies to do this)
Ensure equity and distributive justice (fair and equitable distribution of resources based on need) Develop fair criteria for prioritization
Multiple possible applications
Respect the inherent dignity of all persons Offer vaccine to all; use consistent approach to prioritization decisions
Use the least restrictive means Example of vaccinating schoolchildren to avoid disruptive school closures
Optimize the risk/benefit ratio Maximize the benefit and minimize the risks in prioritization decisions
Work with transparency and accountability Justify prioritization plan and decisions Public and stakeholder consultation
Widespread dissemination of prioritization framework
Additional ethical values from U of T Joint Centre for Bioethics ethical frameworkTable 1 - Footnote 1 *  
Decision-making processes are reasonable, inclusive, responsive Fair criteria, consultation process
Open to review as situation changes
Reciprocity (responsibility of society to support those who face a disproportionate burden in protecting the public good) Prioritization for health care workers
Also reciprocal responsibility of health care workers to report to work and accept vaccine if offered
Trust Build trust with stakeholders before pandemic occurs; ensure that decision-making processes are ethical and transparent
Solidarity Communication and open collaboration with stakeholders
Stewardship Need to consider benefit to the public good and equity

Appendix 3

Potential Vaccination Strategies to Address the National Pandemic Response Goals
Pandemic goal Potential vaccination strategy Potential sub-group priorities
Minimize serious illness and overall deaths Protect individuals against death Health care workers
High-risk persons
Protect individuals against severe illness and complications Health care workers
High-risk persons
Protect individuals against medically attended illness High-risk persons
Whole population
Preserve functioning of the health care system Health care workers
Key health decision-makers
Prevent outbreaks in health care settings Health care workers
Residents of long term care facilities
Family members of long term care residents
Prevent spread of infection to high risk persons Health care workers
Family contacts of high-risk persons
Caregivers of infants and toddlers
Schoolchildren and day care attendees
Minimize societal disruption Maintain societal functioning by vaccinating key groups of individuals Health care workers
Emergency responders
Military
Other societal responders (critical infrastructure)
Key decision-makers
Schoolchildren (to avoid school closures)
Protect the community through herd immunity Schoolchildren and day care attendees

Appendix 4 – Definition of Critical Infrastructure

According to Public Safety Canada, critical infrastructure refers to those physical and information technology facilities, networks, services and assets that if disrupted or destroyed would have a serious impact on the health, safety, security or economic well-being of Canadians or the effective functioning of governments in Canada. The following list indicates the 10 sectors in the National Critical Infrastructure Assurance ProgramFootnote 1 * and provides sample sub-sectors for each sector.

  1. Energy and utilities (e.g. electrical power, natural gas, oil production and transmission systems)
  2. Communications and information technology (e.g. telecommunications, broadcasting systems, software, hardware and networks, including the internet)
  3. Finance (e.g. banking, securities and investment)
  4. Health care (e.g. hospitals, health care and blood supply facilities, laboratories and pharmaceuticals)
  5. Food (e.g. safety, distribution, agriculture and food industry)
  6. Water (e.g. drinking water and wastewater management)
  7. Transportation (e.g. air, rail, marine, surface)
  8. Safety (e.g. chemical, biological, radiological and nuclear safety: hazardous materials; search and rescue; emergency services; and dams)
  9. Government (e.g. services, facilities, information networks, assets and key national sites and monuments)
  10. Manufacturing (e.g. defence industrial base, chemical industry)

National planning for critical infrastructure protection is under way. Some provinces and territories may be using modified definitions of the critical infrastructure sectors, but the concepts are similar. For example, one provincFootnote 2 ** defines nine critical infrastructure sectors as follows (omitting manufacturing and using slightly different groupings):

  1. Electricity
  2. Oil and gas
  3. Government decision-making
  4. Health
  5. Public safety and security
  6. Finance and banking
  7. Telecommunications
  8. Transportation
  9. Food and water

*Public Safety Canada. About Critical Infrastructure. Available at the Public Safety web site. Accessed May 27, 2008.
**Personal communication: Phil Graham, Ontario MOHLTC, April 30, 2008.

Appendix 5 – Goals and Values from the Antiviral Deliberative Dialogue Process

Participants supported three goals:

  • to ensure that normal societal functions are maintained
  • to minimize public fear and panic
  • to reduce serious illness and death during a pandemic.

Priority recipients if antiviral prophylaxis were available:

  • health care workers with close patient contact (general agreement)
  • those in emergency services (opinion divided, especially about other essential services)
  • the most vulnerable, including children, those in institutions, chronically ill and elderly (divided opinion; children most often flagged).

Values emphasized for decision-making:

  • Practicality/efficiency/pragmatism – minimize illness and death, protect health care workers, consider ease of delivery
  • Fairness and equality – consistency across country, avoid inequities of access
  • Compassion for the vulnerable
  • Public awareness/engagement – to gain understanding and support
  • Strong role for government; trust and confidence – government to lead, responsibility to protect vulnerable and workers who will be exposed.

Source: EKOS Research Associates, Inc.Footnote 34

Appendix 6 – Pandemic Vaccine Prioritization Framework: Draft Discussion Tool

Category 1: Scientific Evidence
Criteria Questions Considerations Notes
Disease characteristics and burden How severe is the pandemic?
  • Societal disruption of severe (and moderate?) pandemic might lead to occupational groups being made a higher priority.
  • Pressure to immunize children first in a severe pandemic?
Who is most affected in terms of illness, complications and death?
  • Any ages to target?
  • NACI and/or additional high-risk conditions?
  • Increased occupational risk?
Who are the persons most likely to spread infection?
  • Significant enough to target?
Vaccine characteristics Are there any expected population differences in protection provided by the pandemic vaccine?
  • Adjust priority for groups with expected lower vaccine effectiveness?
Are there any persons who do not need the vaccine?
  • Any ages that appear to be protected?
  • Degree of correlation of history of disease (classical or atypical) to immunity
  • Make any groups totally ineligible for vaccine?
Is there a need for a second dose? Can a reasonable amount of protection be achieved by a single dose?
  • Second dose needed for some or all age groups?
  • Appropriate timing; does this affect prioritization?
Are dose-sparing strategies possible?
  • E.g. intradermal administration?
Are there any vaccine safety concerns?
  • Reconsider risk/benefit for certain ages or population sub-groups
  What is the proposed indication for use and what indication/market authorization has been granted by the health care regulator? What pre-market assessment has been performed and what post-market surveillance requirements are imposed?
  • Consider approved indications (if available)
Category 2: Ethical Considerations
Criteria Questions Considerations Notes
Ethical considerations What ethical principles and values should be applied?
  • Are the ethical principles and values from the CPIP and WHO applicable?
  • Are any of the other ethical frameworks from Canada (e.g. U of T) or elsewhere applicable?
  • To what extent can we extrapolate societal values from the Task Group on Antiviral Prophylaxis or other public consultations?
How do they inform the decision?
  • To what degree should ethical principles prevail over scientific considerations if they do not point in the same direction?
Are the recommendations fair and equitable?
  • What criteria can be used to assess whether they are fair and equitable?
Category 3: Program Considerations
Criteria Questions Considerations Notes
Vaccination strategies What strategies might be considered?
How do the proposed vaccination goals and strategies support the pandemic goals?
  • Translation of the pandemic goals into strategy involves value judgements
  • Are some categories always high priority, e.g. front-line health care workers, persons with underlying health conditions?
Are there important knowledge gaps that affect choice of strategies?
  • Can these be addressed through timely research?
What is the timing of anticipated vaccine availability in relation to pandemic activity?
  • Availability between waves might suggest different priorities than availability at start of second wave
What other factors might affect the strategies?
  • E.g. antiviral use, development of antiviral resistance
Logistical issues What is the rate of vaccine production, release and delivery?
  • Should match prioritization process to vaccine availability
What is the size and anticipated vaccine uptake of each potential priority group?
  • What are most appropriate potential priority groups or settings?
  • Category of societal responders most open to interpretation and P/T variation
  • Possible P/T variation in uptake
Is the target population accessible?
  • Some targets are hard to identify or access – should that affect their prioritization?
  • Need flexibility for some settings (e.g. best to do everyone at once in remote setting)
Program acceptability What are the public and stakeholder values that can inform decisions about vaccine prioritization?
  • High value for prioritizing children early, even if not most severely affected, identified in US planning
Should there be any alterations because of public or provider perceptions of disease severity or risk of vaccine?
  • In severe pandemic public might want children immunized first
  • Concern for risks of untried vaccine, especially in earliest recipients
  • Lower uptake anticipated in mild pandemic
Category 4: Other Policy Considerations
Criteria Questions Considerations Notes
Legal considerations Are there any applicable legal considerations?
  • Examples include departure from manufacturer’s recommendations, use of a vaccine that may be authorized for sale with limited safety and minimal clinical effectiveness data
  • Legal review desirable
Conformity of programs What are other countries doing?
  • How important is this factor? (communications, political considerations)
  • Countries may differ in terms of vaccine availability and pandemic goals and values, but rationales for variation may not be widely known
  • Cross-border issues
What degree of provincial/territorial variation is acceptable?
  • Anticipated variation in essential worker categories
  • What if there is variation in pandemic activity?
  • Cross-border issues
Political considerations Will the proposed prioritization plan be free of controversy, within Canada and in an international context?
  • Will we be criticized for vaccinating everyone if other countries are short of vaccine?
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