Summary of the NACI Seasonal Influenza Vaccine Statement for 2023–2024

Volume 49-10, October 2023: Influenza and Other Respiratory Infections

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Published by: The Public Health Agency of Canada
Issue: Volume 49-10, October 2023: Influenza and Other Respiratory Infections
Date published: October 2023
ISSN: 1481-8531

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Volume 49-10, October 2023: Influenza and Other Respiratory Infections

Advisory Committee Statement

Summary of the National Advisory Committee on Immunization (NACI) Seasonal Influenza Vaccine Statement for 2023–2024

Angela Sinilaite¹, Winnie Siu^1,², Jesse Papenburg^3,4,5,6 on behalf of the National Advisory Committee on Immunization (NACI)

Affiliations

¹ Centre for Immunization Programs, Public Health Agency of Canada, Ottawa, ON

² School of Epidemiology and Public Health, Faculty of Medicine, University of Ottawa, ON

³NACI Influenza Working Group Chair

⁴ Division of Pediatric Infectious Diseases, Department of Pediatrics, Montréal Children’s Hospital of the McGill University Health Centre, Montréal, QC

⁵ Division of Microbiology, Department of Clinical Laboratory Medicine, Optilab Montréal - McGill University Health Centre, Montréal, QC

⁶ Department of Epidemiology, Biostatistics, and Occupational Health, School of Population and Global Health, McGill University, Montréal, QC

Correspondence

naci-ccni@phac-aspc.gc.ca

Suggested citation

Sinilaite A, Siu W, Papenburg J, on behalf of the National Advisory Committee on Immunization (NACI). Summary of the National Advisory Committee on Immunization (NACI) Seasonal Influenza Vaccine Statement for 2023–2024. Can Commun Dis Rep 2023;49(10):406–12. https://doi.org/10.14745/ccdr.v49i10a01

Keywords: National Advisory Committee on Immunization, NACI, influenza, influenza vaccine, guidance

Abstract

Background: The National Advisory Committee on Immunization (NACI) reviews the evolving evidence on influenza immunization and provides annual recommendations regarding the use of seasonal influenza vaccines. The NACI Statement on Seasonal Influenza Vaccine for 2023–2024 updates the 2022–2023 NACI recommendations.

Objective: To summarize the 2023–2024 NACI seasonal influenza vaccine recommendations and to highlight new and updated information.

Methods: In the preparation of the Statement on Seasonal Influenza Vaccine for 2023–2024, the NACI Influenza Working Group applied the NACI evidence-based process to critically appraise the available evidence and to propose recommendations. The recommendations were then considered and approved by NACI in light of the available evidence.

Results: Key changes for the 2023–2024 season include: 1) incorporation of updated information/guidance on influenza vaccination in the context of the coronavirus disease 2019 (COVID-19); 2) new recommendations for Flucelvax^® Quad and Influvac^® Tetra, the two quadrivalent inactivated influenza vaccines with expanded paediatric age indications; and 3) an update to the format of the Statement.

Conclusion: Overall, NACI continues to recommend that an age-appropriate influenza vaccine should be offered annually to all individuals aged six months and older who do not have a contraindication to the vaccine, with particular focus on the groups for whom influenza vaccination is particularly recommended.

Introduction

In Canada, seasonal influenza epidemics generally occur in the late fall and winter months and can lead to significant morbidity and mortality^{Footnote 1}. The burden of influenza varies from year to year and some groups, including young children (younger than six years of age), older adults (65 years of age and older), people with chronic health conditions, pregnant individuals and Indigenous peoples are at higher risk of experiencing severe illness, complications or worsening of chronic health conditions. Influenza vaccination is a critical tool to mitigate ongoing health system stress through protection against influenza-related disease.

The National Advisory Committee on Immunization (NACI) provides the Public Health Agency of Canada (PHAC) with annual recommendations regarding the use of authorized seasonal influenza vaccines, which reflect identified changes in influenza epidemiology, immunization practises and influenza vaccine products available for use in Canada. The annual update of the NACI statement on seasonal influenza vaccine is led by the NACI Influenza Working Group (IWG) and involves a thorough review and evaluation of the literature as well as discussion and debate at the scientific and clinical practice levels. On May 31, 2023, PHAC released new guidance from NACI on the use of seasonal influenza vaccines for the 2023–2024 season, which is based on current evidence and expert opinion. This article provides a concise summary of NACI’s recommendations and supporting information for the 2023–2024 influenza season, including conclusions from evidence reviews on two quadrivalent inactivated influenza vaccines with expanded age indications in children six months of age and older. Updated NACI guidance on concurrent administration of influenza vaccines with the coronavirus disease 2019 (COVID-19) vaccines is also highlighted. Complete details are available in the new NACI Advisory Committee Statement on Seasonal Influenza Vaccine for 2023–2024 (the Statement) on the PHAC website^{Footnote 2}.

Methods

When preparing the Statement on Seasonal Influenza Vaccine for 2023–2024, the NACI IWG identified the need for evidence reviews for new topics, reviewed and analyzed the available evidence, and proposed updated recommendations according to the NACI evidence-based process for developing recommendations^{Footnote 3}. Further details regarding the strength of NACI recommendations are available in Table A1 in the Appendix. NACI’s peer-reviewed framework and evidence-informed tools (including the Ethics Integrated Filters, Equity Matrix, Feasibility Matrix, and Acceptability Matrix) were applied to help ensure that issues related to ethics, equity, feasibility and acceptability are systematically assessed and integrated into NACI guidance^{Footnote 4}.

Results

New or updated information for 2023–2024

The 2023–2024 Statement includes updated information and guidance on influenza in the context of COVID-19, including an overview of changes in influenza epidemiology over the course of the COVID-19 pandemic and updated content on concurrent administration of influenza vaccines with COVID-19 vaccines. NACI guidance states that administration of COVID-19 vaccines may occur at the same time as, or at any time before or after, influenza immunization (including all parenteral and intranasal seasonal influenza vaccines) for individuals six months of age and older. Updated NACI guidance and additional information on concurrent administration of COVID-19 vaccines with influenza vaccines and across all eligible age groups is available in the COVID-19 vaccines: Canadian Immunization Guide chapter^{Footnote 5}.

For the 2023–2024 influenza season, NACI reviewed the available evidence and developed updated recommendations for:

Flucelvax^® Quad, a mammalian cell culture-based influenza vaccine (IIV4-cc)
Influvac^® Tetra, an egg-based, standard dose influenza vaccine (IIV4-SD)

NACI provided the following new recommendations based on a review and analysis of Health Canada assessments of supporting clinical trial evidence submitted by the manufacturers:

NACI recommends that Flucelvax Quad may be considered among the quadrivalent influenza vaccines offered to adults and children six months of age and older (Discretionary NACI Recommendation)
NACI recommends that Influvac Tetra may be considered among the standard dose inactivated quadrivalent influenza vaccines offered to individuals three years of age and older (Discretionary NACI Recommendation)

At this time, NACI concludes that there is insufficient evidence for recommending vaccination with Influvac Tetra in children younger than three years of age (Discretionary NACI Recommendation).

NACI will continue to monitor the evidence as it emerges, and update recommendations as needed. To improve readability and access to information, the format and structure of the Statement has been updated from previous seasons’ statements. Notably, clinical information on seasonal influenza vaccine administration for vaccine providers is now contained in the new Influenza vaccines chapter of the Canadian Immunization Guide^{Footnote 6}.

Summary of National Advisory Committee on Immunization recommendations for the use of influenza vaccines for the 2023–2024 influenza season

NACI continues to recommend influenza vaccination to anyone six months and older who does not have a contraindication to the vaccine. Vaccination should be offered as a priority to people at high risk of influenza-related complications or hospitalization, people capable of transmitting influenza to those at high risk of complications, and others as indicated in List 1.

**List 1: Groups for whom influenza vaccination is particularly recommended**
People at high risk of influenza-related complications or hospitalization All children 6–59 months of age Adults and children with the following chronic health conditions^{Footnote a}: Cardiac or pulmonary disorders (includes bronchopulmonary dysplasia, cystic fibrosis and asthma) Diabetes mellitus and other metabolic diseases Cancer, immune compromising conditions (due to underlying disease, therapy, or both, such as solid organ transplant or hematopoietic stem cell transplant recipients) Renal disease Anemia or hemoglobinopathy Neurologic or neurodevelopment conditions (includes neuromuscular, neurovascular, neurodegenerative, neurodevelopmental conditions and seizure disorders [and, for children, includes febrile seizures and isolated developmental delay], but excludes migraines and psychiatric conditions without neurological conditions)^{Footnote b} Morbid obesity (body mass index of 40 kg/m² and over) Children six months to 18 years of age undergoing treatment for long periods with acetylsalicylic acid, because of the potential increase of Reye’s syndrome associated with influenza All individuals who are pregnant People of any age who are residents of nursing homes and other chronic care facilities Adults 65 years of age and older Indigenous peoples People capable of transmitting influenza to those at high risk Healthcare and other care providers in facilities and community settings who, through their activities, are capable of transmitting influenza to those at high risk Household contacts, both adults and children, of individuals at high risk, whether or not the individual at high risk has been vaccinated: Household contacts of individuals at high risk Household contacts of infants less than six months of age, as these infants are at high risk but cannot receive influenza vaccine Members of a household expecting a newborn during the influenza season Those providing regular childcare to children 0–59 months of age, whether in or out of the home Those who provide services within closed or relatively closed settings to people at high risk (e.g. crew on a cruise ship) Others People who provide essential community services People who are in direct contact with poultry infected with avian influenza during culling operations
Footnote a Refer to Immunization of Persons with Chronic Diseases and Immunization of Immunocompromised Persons in Part 3 of the CIG for additional information about vaccination of people with chronic diseases (7) Return to footnote a referrer Footnote b Refer to the NACI Statement on Seasonal Influenza Vaccine for 2018–2019^{Footnote 8} for rationale supporting the decision to include persons with neurologic or neurodevelopment conditions among the groups for whom influenza vaccination is particularly recommended and the Literature Review on Individuals with Neurologic or Neurodevelopment Conditions and Risk of Serious Influenza-Related Complications^{Footnote 9} for additional details of the evidence reviews that were conducted Return to footnote b referrer Source: Source: List reproduced from NACI Seasonal Influenza Vaccine Statement for 2023–2024^{Footnote 2}

Recommended influenza vaccine options by age group, and recommended dose and route of administration of influenza vaccine types by age, are summarized in Table 1 and Table 2 respectively.

Table 1: Recommendations on choice of influenza vaccine type for individual and public health program-level decision making by age group
Recipient by age group	Vaccine types authorized^{Footnote a}^{Footnote b} for use	Recommendations on choice of influenza vaccine
6–23 months	IIV3-Adj IIV4-SD IIV4-cc	A quadrivalent influenza vaccine licensed for this age group should be used in infants and young children without contraindications, given the burden of influenza B disease in this age group and the potential for lineage mismatch between the predominant circulating strain of influenza B and the strain in a trivalent vaccine Currently, there is insufficient evidence for recommending vaccination with Influvac Tetra (IIV4-SD) in children younger than 3 years of age If a quadrivalent vaccine is not available, a trivalent vaccine licensed for this age group should be used
2–17 years^{Footnote c}	IIV4-SD IIV4-cc LAIV4	An age-appropriate quadrivalent influenza vaccine (IIV4-SD, IIV4-cc or LAIV4) should be used in children without contraindications or precautions (see text below applicable to LAIV), including those with chronic health conditions, given the burden of influenza B disease in this age group and the potential for lineage mismatch between the predominant circulating strain of influenza B and the strain in a trivalent vaccine Currently, there is insufficient evidence for recommending vaccination with Influvac Tetra (IIV4-SD) in children younger than 3 years of age LAIV4 may be given to children with: Stable, non-severe asthma Cystic fibrosis who are not being treated with immunosuppressive drugs (e.g. prolonged systemic corticosteroids) Stable HIV infection, if the child is currently being treated with ART (i.e. HAART) and has adequate immune function LAIV should not be used in children or adolescents for whom it is contraindicated or for whom there are warnings and precautions such as those with: Severe asthma (defined as currently on oral or high dose inhaled glucocorticosteroids or active wheezing) Medically attended wheezing in the seven days prior to vaccination Current receipt of aspirin or aspirin-containing therapy Immune compromising conditions, with the exception of stable HIV infection (i.e. if the child is treated with HAART for at least 4 months and has adequate immune function) Pregnancy In pregnancy, IIV4-SD or IIV4-cc should be used instead
18–59 years	IIV4-SD IIV4-cc RIV4 LAIV4	Any of the available influenza vaccines authorized for this age group should be used in adults 18–59 years of age without contraindications or precautions, noting the following consideration and exceptions: There is some evidence that IIV may provide better efficacy than LAIV in healthy adults LAIV is not recommended for: Pregnant individuals In pregnancy, IIV4-SD, IIV4-cc or RIV4 should be used instead Adults with any of the chronic health conditions identified in List 1, including immune compromising condition Healthcare workers
60–64 years	IIV4-SD IIV4-cc RIV4	Any of the available influenza vaccines authorized for this age group should be used in adults 60–64 years of age without contraindications
65 years and older^{Table 2 footnote c}	IIV3-Adj IIV4-SD IIV4-HD IIV4-cc RIV4	Individual-level decision-making	Public health program-level decision-making
65 years and older^{Table 2 footnote c}	IIV3-Adj IIV4-SD IIV4-HD IIV4-cc RIV4	IIV-HD should be used over IIV-SD, given the burden of influenza A(H3N2) disease and the good evidence of IIV3-HD providing better protection compared to IIV3-SD in adults 65 years of age and older Other than a recommendation for using IIV-HD over IIV-SD formulations, NACI has not made comparative individual-level recommendations on the use of the other available vaccines in this age group. In the absence of a specific product, any of the available age-appropriate influenza vaccines should be used	Any of the available influenza vaccines authorized in this age group should be used There is insufficient evidence on the incremental value of different influenza vaccines (i.e. cost-effectiveness assessments have not been performed by NACI) to make comparative public health program-level recommendations on the use of the available vaccines
Table 1 Abbreviations Abbreviations: ART, antiretroviral therapy; HAART, highly active antiretroviral therapy; IIV, inactivated influenza vaccine; IIV3-Adj, adjuvanted trivalent inactivated influenza vaccine; IIV3-HD, high-dose trivalent inactivated influenza vaccine; IIV4-cc, quadrivalent mammalian cell-culture based inactivated influenza vaccine; IIV4-HD, high-dose quadrivalent inactivated influenza vaccine; IIV4-SD, standard-dose quadrivalent inactivated influenza vaccine; LAIV, live attenuated influenza vaccine; LAIV4, quadrivalent live attenuated influenza vaccine; NACI, National Advisory Committee on Immunization; RIV4, quadrivalent recombinant influenza vaccine Table 1 Footnote a IIV3-SD formulation will not be authorized or available for use in Canada during the 2023–2024 influenza season Table 1 Return to footnote a referrer Table 1 Footnote b IIV3-HD formulations will not be authorized or available for use in Canada during the 2023–2024 influenza season Table 1 Return to footnote b referrer Table 1 Footnote c Refer to Table 3 of the NACI Seasonal Influenza Vaccine Statement for 2023–2024 for a summary of vaccine characteristics of LAIV compared with IIV in children 2–17 years of age Table 1 Return to footnote c referrer Table 1 Footnote d Refer to Table 4 of the NACI Seasonal Influenza Vaccine Statement for 2023–2024 for a comparison of the vaccine characteristics of influenza vaccine types available for use in adults 65 years of age and older Table 1 Return to footnote d referrer Table 1 Source Source: Table reproduced from NACI Seasonal Influenza Vaccine Statement for 2023–2024^{Footnote 2}

Table 2: Recommended dose and route of administration, by age, for influenza vaccine types authorized for the 2023–2024 influenza season
Age group	Influenza vaccine type (route of administration)						Number of doses required
Age group	IIV4-SD^{Table 2 footnote a} (IM)	IIV4-cc^{Table 2 footnote b} (IM)	IIV3-Adj^{Table 2 footnote c} (IM)	IIV4-HD^{Table 2 footnote d} (IM)	RIV4^{Table 2 footnote e} (IM)	LAIV4^{Table 2 footnote f} (intranasal)	Number of doses required
6–23 months	0.5 mL^{Table 2 footnote g}	–	0.25 mL	–	–	–	1 or 2^{Table 2 footnote h}
2–8 years	0.5 mL	0.5 mL	–	–	–	0.2 mL (0.1 mL per nostril)	1 or 2^{Table 2 footnote h}
9–17 years	0.5 mL	0.5 mL	–	–	–	0.2 mL (0.1 mL per nostril)	1
18–59 years	0.5 mL	0.5 mL	–	–	0.5 mL	0.2 mL (0.1 mL per nostril)	1
60–64 years	0.5 mL	0.5 mL	–	–	0.5 mL	–	1
65 years and older	0.5 mL	0.5 mL	0.5 mL	0.7 mL	0.5 mL	–	1
Table 2 footnotes Table 2 - Abbreviations Abbreviations: IIV3-Adj, adjuvanted trivalent inactivated influenza vaccine; IIV4-cc, quadrivalent mammalian cell culture based inactivated influenza vaccine; IIV4-HD, high-dose quadrivalent inactivated influenza vaccine; IIV4-SD, standard-dose quadrivalent inactivated influenza vaccine; IM, intramuscular; LAIV4, quadrivalent live attenuated influenza vaccine; RIV4, quadrivalent recombinant influenza vaccine Table 2 footnote a Afluria^® Tetra (5 years and older), Flulaval^® Tetra (6 months and older), Fluzone^® Quadrivalent (6 months and older), Influvac^® Tetra (3 years and older) Return to first Table 2 footnote a referrer Table 2 footnote b Flucelvax^® Quad (6 months and older) Return to first Table 2 footnote b referrer Table 2 footnote c Fluad Pediatric^® (6–23 months) or Fluad^® (65 years and older) Return to first Table 2 footnote c referrer Table 2 footnote d Fluzone^® High-Dose Quadrivalent (65 years and older) Return to first Table 2 footnote d referrer Table 2 footnote e Supemtek™ (18 years and older) Return to first Table 2 footnote e referrer Table 3 footnote f FluMist^® Quadrivalent (2–59 years) Return to first Table 2 footnote f referrer Table 2 footnote g Evidence suggests moderate improvement in antibody response in infants, without an increase in reactogenicity, with the use of full-vaccine doses (0.5 mL) for unadjuvanted inactivated influenza vaccines ^{Footnote 10} ^{Footnote 11}. This moderate improvement in antibody response without an increase in reactogenicity is the basis for the full dose recommendation for unadjuvanted inactivated vaccine for all ages. For more information, refer to Statement on Seasonal Influenza Vaccine for 2011–2012^{Footnote 12} Return to first Table 2 footnote g referrer Table 2 footnote h Children six months to less than nine years of age receiving seasonal influenza vaccine for the first time in their life should be given two doses of influenza vaccine, with a minimum interval of four weeks between doses. Children six months to less than nine years of age who have been properly vaccinated with one or more doses of seasonal influenza vaccine in the past should receive one dose of influenza vaccine per season thereafter Return to first Table 2 footnote h referrer Table 2 - Source Source: Table reproduced from NACI Seasonal Influenza Vaccine Statement for 2023–2024 ^{Footnote 2}

Conclusion

NACI continues to recommend annual influenza vaccination for all individuals aged six months and older (noting product-specific age indications and contraindications). Influenza vaccination is particularly important for people at high risk of influenza-related complications or hospitalization; people capable of transmitting influenza to those at high risk; people who provide essential community services; and people in direct contact during culling operations with poultry infected with avian influenza. For the 2023–2024 influenza season, NACI advises that: 1) Flucelvax^® Quad may be considered among the quadrivalent influenza vaccines offered to adults and children six months of age and older and 2) Influvac^® Tetra may be considered among the standard dose inactivated quadrivalent influenza vaccines offered to individuals three years of age and older.

Authors’ statement

AS — Writing, original draft, review, editing

WS — Writing, review, editing

JP — Review, editing

The NACI Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2023–2024 was prepared by A Sinilaite, A Gil, W Siu and J Papenburg, on behalf of the NACI Influenza Working Group, and was approved by NACI.

Competing interests

J Papenburg reports grants to his institution from MedImmune and Merck and personal fees from AstraZeneca and Merck, all of which were outside of the submitted work.

Acknowledgements

Influenza Working Group members: J Papenburg (Chair), P De Wals, D Fell, I Gemmill, R Harrison, J Langley, A McGeer, and D Moore.

Former members: N Dayneka, K Klein, D Kumar, J McElhaney, and S Smith.

NACI members: S Deeks (Chair), R Harrison (Vice-Chair), J Bettinger, N Brousseau, P De Wals, E Dubé, V Dubey, K Hildebrand, K Klein, J Papenburg, A Pham-Huy, C Rotstein, B Sander, S Smith, and S Wilson.

Liaison representatives: L Bill (Canadian Indigenous Nurses Association), LM Bucci (Canadian Public Health Association), E Castillo (Society of Obstetricians and Gynaecologists of Canada), A Cohn (Centers for Disease Control and Prevention, United States), L Dupuis (Canadian Nurses Association), P Emberley (Canadian Pharmacists Association), J Emili (College of Family Physicians of Canada), D Fell (Canadian Association for Immunization Research and Evaluation), S Funnel (Indigenous Physicians Association of Canada), J Hu (College of Family Physicians of Canada), N Ivers (College of Family Physicians of Canada), M Lavoie (Council of Chief Medical Officers of Health), D Moore (Canadian Paediatric Society), M Naus (Canadian Immunization Committee), A Pham-Huy (Association of Medical Microbiology and Infectious Disease Canada), and A Ung (Canadian Pharmacists Association).

Ex-officio representatives: V Beswick-Escanlar (National Defence and the Canadian Armed Forces), E Henry (Centre for Immunization and Respiratory Infectious Diseases [CIRID], PHAC), M Lacroix (Public Health Ethics Consultative Group, PHAC), C Lourenco (Biologic and Radiopharmaceutical Drugs Directorate, Health Canada [HC]), D MacDonald (CIRID, PHAC), S Ogunnaike-Cooke (CIRID, PHAC), G Poliquin (National Microbiology Laboratory, PHAC), K Robinson (Marketed Health Products Directorate, HC) and T Wong (First Nations and Inuit Health Branch, Indigenous Services Canada).

The NACI acknowledges and appreciates the contribution of F Crane, P Doyon-Plourde, C Tremblay, M Tunis, C Williams, M Xi, K Gusic and J Zafack to this statement.

Funding

The work of the National Advisory Committee on Immunization is supported by the Public Health Agency of Canada.

References

Footnote 1

Statistics Canada. The 10 leading causes of death, 2011. Ottawa, ON: StatCan; 2018. http://www.statcan.gc.ca/pub/82-625-x/2014001/article/11896-eng.htm

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Footnote 2

National Advisory Committee on Immunization. Statement on Seasonal Influenza Vaccine for 2023–2024. Ottawa, ON: PHAC; 2023. https://www.canada.ca/en/public-health/services/publications/vaccines-immunization/national-advisory-committee-immunization-statement-seasonal-influenza-vaccine-2023-2024.html

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Footnote 3

National Advisory Committee on Immunization. Evidence-based recommendations for immunization— Methods of the National Advisory Committee on Immunization. Can Commun Dis Rep 2009;35(ACS-1):1-10. https://www.canada.ca/content/dam/phac-aspc/migration/phac-aspc/publicat/ccdr-rmtc/09pdf/ccdr-rmtc-vol-35-acs-dcc-1.pdf

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Footnote 4

Ismail SJ, Hardy K, Tunis MC, Young K, Sicard N, Quach C. A framework for the systematic consideration of ethics, equity, feasibility, and acceptability in vaccine program recommendations. Vaccine 2020;38(36):5861–76. https://doi.org/10.1016/j.vaccine.2020.05.051

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Footnote 5

Public Health Agency of Canada. COVID-19 vaccine: Canadian Immunization Guide. Ottawa, ON: PHAC; 2023. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-26-covid-19-vaccine.html

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Footnote 6

Public Health Agency of Canada. Influenza vaccines: Canadian Immunization Guide. Ottawa, ON: PHAC; 2023. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-10-influenza-vaccine.htm

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Footnote 7

Public Health Agency of Canada. Canadian Immunization Guide: Part 3. Vaccination of specific populations. Ottawa, ON: PHAC; 2015. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-3-vaccination-specific-populations.html

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Footnote 8

National Advisory Committee on Immunization (NACI). Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2018–2019. Ottawa, ON: PHAC; 2017. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-statement-seasonal-influenza-vaccine-2018-2019.html

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Footnote 9

National Advisory Committee on Immunization (NACI). Literature Review on Individuals with Neurologic and Neurodevelopment Conditions and Risk of Serious Influenza-Related Complications. Ottawa, ON: PHAC; 2018. https://www.canada.ca/en/public-health/services/publications/healthy-living/executive-summary-literature-review-individuals-neurologic-neurodevelopment-conditions-risk-serious-influenza-related-complications.html

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Footnote 10

Schanzer DL, McGeer A, Morris K. Statistical estimates of respiratory admissions attributable to seasonal and pandemic influenza for Canada. Influenza Other Respir Viruses 2013;7(5):799–808. https://doi.org/10.1111/irv.12011

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Footnote 11

Schanzer DL, Sevenhuysen C, Winchester B, Mersereau T. Estimating influenza deaths in Canada, 1992-2009. PLoS One 2013;8(11):e80481. https://doi.org/10.1371/journal.pone.0080481

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Footnote 12

National Advisory Committee on Immunization. NACI Statement: Seasonal Influenza Vaccine, 2011-2012. Can Commun Dis Rep 2011;37(ACS-5). https://www.canada.ca/en/public-health/services/reports-publications/canada-communicable-disease-report-ccdr/monthly-issue/2011-37/canada-communicable-disease-report-acs-5.html

Return to Footnote 12 referrer

Appendix

Table A1: Strength of the National Advisory Committee on Immunization recommendations
Strength of NACI recommendation (based on factors not isolated to strength of evidence, e.g. public health need)	Strong	Discretionary
Wording	"should/should not be offered"	"may be considered"
Rationale	Known/anticipated advantages outweigh known/anticipated disadvantages ("should"), OR known/anticipated disadvantages outweigh known/anticipated advantages ("should not")	Known/anticipated advantages closely balanced with known/anticipated disadvantages, OR uncertainty in the evidence of advantages and disadvantages exists
Implication	A strong recommendation applies to most populations/individuals and should be followed unless a clear and compelling rationale for an alternative approach is present	A discretionary recommendation may be considered for some populations/individuals in some circumstances Alternative approaches may be reasonable
Table A1 footnote Table A1 - abbreviation Abbreviation: NACI, National Advisory Committee on Immunization

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