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Varicella (chickenpox) vaccines: Canadian Immunization Guide

For health professionals

Notice

This chapter has not yet been updated with the following guidance from the National Advisory Committee on Immunization (NACI):

Last partial content update (see table of updates): April 2025


Last complete chapter revision: September 2016

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Key information

What

Who

How

Why

Epidemiology

Disease description

Infectious agent

Varicella (chickenpox) is a generalized viral disease caused by varicella zoster virus (VZV), a deoxyribonucleic acid (DNA virus) of the Herpesvirus family. For additional information about VZV, refer to the Pathogen Safety Data Sheet.

Reservoir

Humans

Transmission

VZV is spread by the airborne route, as well as by direct contact with virus shed from skin lesions. The attack rate among susceptible contacts in household settings is estimated at 65% to 87%. The incubation period is from 10 to 21 days after exposure, usually 14 to 16 days. Infectiousness begins 1 to 2 days before onset of the rash and lasts until the last lesion has crusted.

Risk factors

Risk of varicella infection severity increases with age. Although in healthy children varicella is considered to be a relatively benign disease, serious complications can occur.

Persons at increased risk of severe varicella

The following groups of individuals are considered to be at increased risk of severe varicella:

Seasonal and temporal patterns

The number of varicella disease cases increases during the school year and decreases sharply during summer vacation.

Spectrum of clinical illness

Symptoms of varicella include low-grade fever, mild constitutional symptoms, and a generalized, pruritic rash, with lesions at different stages that progress rapidly from macules to papules to vesicular lesions before crusting. The main complications of varicella include secondary bacterial skin and soft tissue infections, bacteremia, pneumonia, osteomyelitis, septic arthritis, necrotizing fasciitis, toxic shock-like syndrome, cerebellar ataxia, stroke and encephalitis. Varicella increases the risk of severe invasive group A streptococcal infection in previously healthy children by 40-fold to 60-fold. Complications are more common in adolescents, adults and people with conditions that compromise their immune system, in whom there are higher rates of pneumonia, encephalitis and death.

Congenital varicella syndrome is rare when infection occurs before the 13 or after the 20 weeks of gestation. The risk is approximately 2% when infection occurs between 13 and 19 weeks of gestation. Congenital infection results in a wide clinical spectrum, which may include low birth weight, ophthalmic abnormalities, skin scarring, limb atrophy, cerebral atrophy and a variety of other anomalies. Maternal varicella occurring in the 5 days before to 2 days after birth is associated with severe neonatal varicella in 17% to 30% of infants, with high case fatality for the newborn.

Disease distribution

In countries without vaccination programs, varicella is mainly a disease of childhood, developing in 50% of children by the age of 5 years and 90% by the age of 12 years. In the pre-vaccine era, approximately 350,000 varicella cases and 1,500 to 2,000 varicella-related hospitalizations occurred each year in Canada. Since the introduction of immunization programs in Canada, there has been a decrease in the burden of varicella.

For more information about varicella disease, including disease description, distribution and epidemiology, refer to the Varicella (Chickenpox) website.

Preparations authorized for use in Canada

Varicella-containing vaccines

Varicella zoster immunoglobulin

For complete prescribing information, consult the product leaflet or information contained within the product monograph available through Health Canada's Drug Product Database.

Refer to Contents of immunizing agents authorized for use in Canada in Part 1 for lists of vaccines and passive immunizing agents authorized for use in Canada and their contents.

Immunogenicity, efficacy and effectiveness

Immunogenicity

In healthy children 12 months to 12 years of age, a single univalent varicella vaccine dose results in a seroconversion rate of 98% at 4 to 6 weeks after vaccination, with antibodies persisting in 98% at 5 years and 96% at 7 years after vaccination. A second dose of a univalent varicella vaccine in children produces an improved immunologic response that is correlated with improved protection. In adults and adolescents 13 years of age and older, 2 vaccine doses administered 4 to 8 weeks apart result in seroconversion rates of 99% at 4 to 6 weeks after the second dose, with persistence of antibodies 5 years later in 97% of vaccine recipients.

In 12 month old children, a single dose of MMRV vaccine results in similar seroconversion rates and geometric mean titres as those achieved after concomitant administration of measles-mumps-rubella (MMR) vaccine and univalent varicella vaccine. For additional information about the immunogenicity of MMRV vaccine, refer to Measles vaccines.

Efficacy and effectiveness

The rate of breakthrough varicella disease in vaccine recipients following 1 dose of univalent varicella vaccine has been estimated at 7.2% over a 10 year follow-up period. A 2 dose primary schedule for children 12 months to 12 years of age has shown to reduce the cumulative risk of breakthrough disease 3.3-fold compared to children who received only 1 dose. The estimated vaccine effectiveness 10 years following the receipt of 2 doses of univalent varicella vaccine is estimated at over 98% against any varicella disease and 100% against severe varicella.

There are no data regarding the long-term effectiveness of MMRV vaccine.

Recommendations for use

Healthy children (12 months to less than 18 years of age)

Schedule

Routine schedule
Healthy children (12 months to less than 13 years of age)

For routine immunization of children aged 12 months to less than 13 years, 2 doses of varicella-containing vaccine, using either univalent varicella or MMRV vaccine, should be administered. The first varicella-containing vaccine dose should be administered at 12 to 15 months of age and the second dose at 18 months of age or any time thereafter, but no later than around school entry. The recommended interval between 2 doses is 3 months.

The optimal interval between doses will depend on the goal of the immunization program. If the goal of immunization is to achieve higher antibody levels to prevent breakthrough disease among preschool age children, the second dose of the varicella-containing vaccine should be provided closer to the first dose (for example at 12 and 15 months of age, or at 12 and 18 months of age). Alternatively, reduction of primary vaccine failure among school age children is likely to be better achieved by providing the second dose of a varicella-containing vaccine closer to school entry (4 to 6 years of age).

Children with a history of varicella disease occurring before 12 months of age should receive routine immunization with 2 doses of varicella-containing vaccine after 12 months of age, because varicella disease at less than 12 months of age has been associated with an increased risk of a second episode of varicella. Children who receive 1 dose of varicella-containing vaccine and subsequently develop laboratory confirmed breakthrough infection do not require a second dose of a varicella-containing vaccine for varicella protection.

Catch-up and accelerated schedules
Children (12 months to less than 13 years of age)

Two doses of varicella-containing vaccine, using either univalent varicella or MMRV vaccine, should be administered to children less than 13 years of age who were not immunized on the routine schedule. For preschool aged children, 2 doses of varicella-containing vaccine should be administered before school entry (4 to 6 years of age). Although the recommended routine interval between doses for children less than 13 years of age is 3 months, when rapid protection is required, a minimum interval of 4 weeks may be used.

Adolescents (13 to less than 18 years of age)

Adolescents without contraindications who do not meet the definition for varicella immunity (refer to susceptibility and immunity for a definition of susceptible) should receive 2 doses of a univalent varicella vaccine, as MMRV is not authorized for use in this age group. In adolescents with documentation of having received only 1 dose of a varicella-containing vaccine, a second dose should be offered. The recommended interval between two varicella-containing vaccines is 6 weeks for individuals 13 years of age and older. The minimum interval between doses is 4 weeks.

Refer to Timing of vaccine administration in Part 1 for additional information about delayed immunization schedules and accelerated immunization schedules.

Healthy adults (18 years of age and older)

Adults less than 50 years of age

Adults less than 50 years of age without contraindications who do not meet the definition for varicella immunity (refer to Susceptibility and immunity) should receive 2 doses of univalent varicella vaccine, as MMRV is not authorized for use in this age group. The minimum interval between doses is 4 weeks.

Susceptible women of childbearing age are considered to be a priority for varicella immunization because varicella-containing vaccine should not be given during pregnancy. Adults less than 50 years of age who have received only 1 dose of varicella vaccine should be offered a second dose.

Adults 50 years of age and older

In the rare circumstance that an adult 50 years of age and over is known to be serologically susceptible to varicella based on previous laboratory testing, the individual should be vaccinated with 2 doses of univalent varicella vaccine. The minimum interval between doses is 4 weeks. For other adults 50 years of age and over, refer to Herpes zoster (shingles) vaccine.

Refer to Immunization of adults in Part 3 for additional information about routinely recommended immunization for adults as well as vaccines recommended for adults in specific risk situations. Refer to Timing of vaccine administration for additional information about delayed immunization schedules and accelerated immunization schedules.

Susceptibility and immunity

Individuals who have ANY of the following are considered immune to varicella:

If varicella occurred before the year of a one-dose vaccine program implementation (refer to table 1), a self-reported history or health care provider diagnosis is considered a reliable correlate of immunity for healthy individuals, including pregnant women without significant exposure to VZV (refer to significant exposures to VZV) and health care workers (HCW) who are currently or have previously been employed in a Canadian health care setting. In general, healthy adults 50 years of age and older, are presumed to be immune to varicella, even if the person does not remember having had chickenpox or herpes zoster (shingles, HZ).

If varicella occurred after the year of a one-dose immunization program implementation (refer to table 1), a self-reported history or health care provider diagnosis cannot be considered a reliable correlate of immunity because one-dose immunization programs had a marked impact on the prevalence of wild-type varicella. A self-reported history or diagnosis of varicella or HZ by a health care provider is not considered an acceptable evidence of immunity for:

Recipients of a hematopoietic stem cell transplant (HSCT) should be considered susceptible in the post-transplantation period, regardless of a pre-transplant history of vaccination, positive serologic results or varicella or HZ disease. For the purposes of post-exposure prophylaxis, an immunosuppressed person with a negative antibody test should be considered as susceptible.

Table 1: Implementation of one dose varicella immunization programs in Canadian provinces and territories
Province or territory Year of program implementation
Prince Edward Island 2000
Alberta 2001
Northwest Territories 2001
Nova Scotia 2002
Nunavut 2002
Ontario 2004
New Brunswick 2004
Manitoba 2004
Newfoundland and Labrador 2005
Saskatchewan 2005
British Columbia 2005
Quebec 2006
Yukon 2007

Booster doses and re-immunization

Booster doses beyond the 2 recommended doses of varicella-containing vaccines are not necessary.

Post-exposure immunization and outbreak control (refer to table 2)

Infection with VZV may occur as a result of contact with a person with varicella or HZ. Post-exposure immunization may be required depending on the level of exposure to VZV. Post-exposure management of healthy infants less than 12 months of age is not indicated as these infants are generally protected by maternal antibodies. For information about post-exposure serologic testing, refer to serologic testing. For information about post-exposure management in pregnancy, refer to pregnancy and breastfeeding.

Significant exposures to varicella zoster virus

The following situations are considered significant exposures to VZV as result of contact with a person with varicella:

The following situations are considered significant exposures to VZV as result of contact with a person with HZ:

Post-exposure immunization

Univalent varicella vaccine

Univalent varicella vaccine is the post-exposure management of choice for susceptible, healthy, non-pregnant persons. For optimal effectiveness, univalent varicella vaccine should be given as soon as possible, preferably within 72 hours, after exposure. When given up to 5 days after exposure, it has been shown to be approximately 90% effective in preventing or reducing the severity of varicella. Individuals under 50 years of age who have received only 1 dose of varicella-containing vaccine should be offered a second dose. There are no data on the use of MMRV vaccine in varicella post-exposure situations.

Varicella zoster immunoglobulin

Varicella zoster immune globulin (VarIg) is a sterile solution of varicella zoster Ig prepared from the pooled human plasma of screened donors with high titres of antibodies to varicella zoster virus.

The decision to administer VarIg should be based on fulfilling all of the following four criteria:

  1. The exposed person is susceptible to varicella. Refer to susceptibility and immunity.
  2. There has been a significant exposure to a person with varicella or HZ. Refer to significant exposures to VZV.
  3. The exposed person is at increased risk of severe varicella. Refer to persons at increased risk of severe varicella.
  4. Post-exposure immunization with univalent varicella vaccine is contraindicated. Refer to contraindications and precautions.

For maximal benefit, VarIg should be administered as soon as possible following exposure, and ideally within 96 hours after first exposure. In the case of prolonged exposure, the exact timing of transmission may be unknown and therefore it may be used within 96 hours of the most recent exposure. If more than 96 hours but less than 10 days have elapsed since the last exposure, VarIg may be administered to individuals for whom it is indicated; when given more than 96 hours after exposure, its primary purpose may be attenuation rather than prevention of disease. The benefit of administering VarIg after 96 hours is uncertain.

The recommended dose of VarIg is 125 IU/10 kg of body weight up to a maximum of 625 IU. The minimum dose is 125 IU. VarIg should be given by the IM route.

Protection conferred by VarIg lasts approximately 3 weeks. Subsequent exposures occurring more than 3 weeks after a dose of VarIg require additional doses of VarIg if the criteria for administration, as specified above, are met.

Individuals receiving replacement IVIg (400 mg/kg of body weight or higher) are considered protected and do not require VarIg if the last dose of IVIg was received within the three weeks prior to varicella exposure.

If VarIg is being considered, consultation with an infectious diseases or infection control specialist is advised.

For additional information about post-exposure immunization of pregnant women refer to pregnancy and breastfeeding.

Table 2: Varicella post-exposure management for susceptibleTable 2 note 1 individuals
Post-exposure intervention Individual
Healthy, non-pregnant
(12 months of ageTable 2 note 2 and older)		 Pregnant ImmunocompromisedTable 2 note 3
Vaccinate with varicella vaccine Yes No No
Check VZV IgG No Yes Yes
If VZV IgG negative, administer VarIgTable 2 note 4 Not applicable Yes Yes

Table 2 notes

Table 2 note 1

Refer to susceptibility and immunity for definition of susceptible.

Return to table 2 note 1 referrer

Table 2 note 2

Refer to Varicella zoster immunoglobulin for information regarding newborns of mothers who develop varicella from 5 days before until 48 hours after delivery.

Return to table 2 note 2 referrer

Table 2 note 3

In case of hematopoietic stem cell transplant, administer VarIg regardless of VZV IgG result

Return to table 2 note 3 referrer

Table 2 note 4

If serology results cannot be obtained within 96 hours, VarIg should be administered.

Return to table 2 note 4 referrer

 

Table 2 - Abbreviations

VarIg

varicella zoster immunoglobulin

VZV IgG

antibodies to varicella zoster

Outbreak control

Persons exposed to a case of varicella should be a priority for immunization. Post-exposure immunization is useful in preventing or limiting varicella outbreaks in hospitals, child care facilities and homeless shelters. Serologic testing for susceptibility is not necessary prior to immunization in an outbreak situation. There are no data on the use of MMRV vaccine in outbreak situations. For additional information refer to post-exposure immunization.

Vaccination of specific populations

Persons with inadequate immunization records

Children and adults, who are susceptible to varicella, including those lacking adequate documentation of immunization, should be started on an immunization schedule appropriate for their age and risk factors. Varicella-containing vaccine may be given regardless of possible previous receipt of the vaccine, because adverse events associated with repeated immunization have not been demonstrated. Refer to Immunization of persons with inadequate immunization records in Part 3 for additional information.

Pregnancy and breastfeeding

Immunity to varicella should be reviewed in women of reproductive age and vaccination should be recommended to susceptible non-pregnant women. Women should delay pregnancy by at least 4 weeks following vaccination with a univalent varicella vaccine.

Varicella-containing vaccine is contraindicated in pregnancy because there is a theoretical risk to the fetus. However, there is no evidence to demonstrate a teratogenic risk from the vaccine and termination of pregnancy should not be recommended following inadvertent immunization with varicella vaccine on the basis of fetal risks following maternal immunization. Pregnant women who are not immune to varicella should have vaccination offered post-partum.

Following exposure to VZV in pregnancy, pregnant women should be evaluated for a history of varicella vaccination or disease. In the absence of such a history, immunity should be assessed by serologic testing as soon as possible. If serology results cannot be obtained within 96 hours, VarIg should be administered to pregnant women with significant exposure to VZV (refer to significant exposures to VZV) who are presumed to be susceptible (refer to susceptibility and immunity). Univalent varicella vaccine should be provided after delivery, ensuring that the recommended interval has passed since VarIg was administered. For recommendations on the interval between administration of VarIg and vaccination with varicella-containing vaccine, refer to Blood products, human immunoglobulin and timing of immunization in Part 1.

Susceptible individuals, including women who are breastfeeding, living in households expecting a newborn, should be vaccinated with a varicella-containing vaccine according to an age-appropriate schedule.

Refer to Blood products, human immunoglobulin and timing of immunization in Part 1 for information about varicella vaccination of post-partum women who have received Rh immunoglobulin (RhIg). Refer to Immunization in pregnancy and breastfeeding in Part 3 for additional information.

Patients in health care institutions

Most residents of long-term care facilities will be immune to varicella. Post-partum women susceptible to varicella should be vaccinated before discharge. Refer to Immunization of patients in health care institutions in Part 3 for additional information about varicella vaccination of patients in health care institutions.

Persons with chronic diseases

Asplenia or hyposplenia

Susceptible hyposplenic or asplenic (congenital absence, surgical removal or functional [for example, sickle cell disease]) individuals should receive 2 doses of univalent varicella vaccine, at least 3 months apart.

Chronic renal disease and patients on dialysis

Varicella vaccine is recommended for susceptible individuals with chronic renal disease or undergoing dialysis. Two doses of univalent varicella vaccine may be given, at least 3 months apart.

Neurologic disorders

People with conditions such as autism spectrum disorders or demyelinating disorders, including multiple sclerosis should receive all routinely recommended immunizations, including varicella-containing vaccine.

Chronic lung disease

Varicella immunization should be a priority for people with cystic fibrosis because they are at increased risk of complications from varicella infection, which may cause a transient worsening of lung function. Two doses of univalent varicella vaccine may be given, at least 3 months apart.

Chronic inflammatory diseases

Individuals with autoimmune disease not treated with immunosuppressive drugs are not considered significantly immunocompromised and should receive varicella immunization following consultation with their physician. Some rheumatic disease modifying agents such as hydroxychloroquine, sulfasalazine, or auranofin are not considered immunosuppressive, for the purposes of live vaccine administration.

Conditions requiring chronic salicylate therapy

For children and adolescents on chronic salicylate therapy (medications derived from salicylic acid, such as acetylsalicylic acid [ASA]), special consideration must be given when administering varicella vaccines because of an association between wild-type infection, salicylate therapy and Reye's syndrome. Ideally, these individuals should be considered a priority to receive varicella immunization prior to the initiation of chronic salicylate therapy. Refer to drug-drug interactions for additional information regarding salicylate therapy following varicella vaccination.

Refer to Immunization of persons with chronic diseases in Part 3 for additional general information about vaccination of people with chronic diseases.

Immunocompromised persons

Individuals who are immunocompromised, either due to underlying conditions or immunosuppressive agents, are more susceptible to infections including varicella. They may be more likely to experience more severe disease and complications. The safety and effectiveness of the varicella vaccine is determined by the type of immunodeficiency and degree of immunosuppression.

In general, immunocompromised people should not receive live vaccines because of the risk of disease caused by the vaccine strains. When considering immunization of an immunocompromised person with a live vaccine, approval from the individual's attending physician should be obtained before vaccination. For complex cases, referral to a physician with expertise in immunization or immunodeficiency is advised. In cases in which, in the opinion of the physician, the benefits of immunization outweigh the risks, any of the univalent varicella vaccines can be used.

Refer to Immunization of immunocompromised persons in Part 3 and to post-exposure immunization and outbreak control for more information.

Travellers

It is important that people travelling or living abroad be immune to varicella. In tropical climates varicella tends to occur at older ages (compared with temperate climates) and at any time of the year. Refer to Immunization of travellers in Part 3 for additional information about varicella vaccination of travellers.

Persons new to Canada

Health care providers who see persons newly arrived in Canada should review the immunization status and update immunization for these individuals as necessary. People from tropical regions are more likely to be susceptible to varicella and should be a priority for varicella immunization. Refer to Immunization of persons new to Canada in Part 3 for additional information about varicella vaccination of people who are new to Canada.

Workers

Varicella immunization should be a priority for susceptible workers (refer to susceptibility and immunity for a definition of susceptible) including health care workers, child care workers, and teachers of young children. These groups are at occupational risk of exposure or may transmit disease to susceptible individuals. Two doses of varicella vaccine are recommended for susceptible workers, as is the case for all susceptible adults. A second dose of varicella vaccine should be offered to workers who have only received 1 dose of vaccine.

Following the exposure of HCW to varicella within health care settings, verification of susceptibility based on documented evidence of immunization with 2 doses of a varicella-containing vaccine or laboratory evidence of immunity should be a part of post-exposure protocols. All HCW should be immunized with two doses of univalent varicella vaccine when there is uncertainty about immunity to varicella.

Health care workers with a post-vaccine rash at the injection site may continue to work if the rash is covered. As a precaution, those with a varicella-like rash not confined to the injection site should be excluded from work in high-risk patient care areas (for example, where there are premature infants and immunocompromised patients) until lesions are crusted. Vaccine recipients with a post-vaccination varicella-like rash rarely transmit the vaccine-associated virus.

Refer to Immunization of workers in Part 3 for additional information about varicella vaccination of workers.

Serologic testing

Although useful for establishing immunity after wild-type infection, commercially available varicella antibody tests, such as the enzyme-linked immunosorbant assay (ELISA) and latex agglutination (LA), may not have sufficient sensitivity to detect antibody after vaccination. The glycoprotein ELISA (gpELISA) test is more sensitive, but is not routinely available. Previously vaccinated individuals who are inadvertently tested are likely to be immune to varicella, even if there is no detectable antibody.

Pre-immunization

Serologic testing is not recommended for healthy individuals. All healthy individuals who may be susceptible to varicella should be offered immunization with 2 doses of univalent varicella vaccine.

Post-immunization

Serologic testing is not recommended for healthy individuals. Certain immunocompromised individuals who are vaccinated with univalent varicella vaccine may have antibody testing performed 6 to 8 weeks after the last dose.

Post-exposure and outbreak situations

Following significant exposure to VZV (refer to significant exposure to VZV), serologic testing is indicated for susceptible immunocompromised individuals and pregnant women (refer to Susceptibility and immunity), and should be conducted as soon as possible. Healthy individuals that have been previously found to be seropositive do not need to be tested again. HSCT recipients are considered susceptible in the post-transplantation period, regardless of positive serologic results. Refer to outbreak control for additional information regarding immunization in outbreak situations.

Administration practices

Dose

Each dose of varicella vaccine is 0.5 mL.

Route of administration

Univalent varicella vaccine should be administered subcutaneously (SC). Although the intramuscular (IM) route is not recommended, there is evidence that it is not necessary to repeat a dose of univalent varicella vaccine if it is inadvertently given IM. MMRV vaccine should be administered SC or IM. Refer to Vaccine administration practices in Part 1 for additional information.

Interchangeability of vaccines

For a 2 dose schedule, it is recommended that the same manufacturer's univalent varicella vaccine or MMRV vaccine be used to complete the schedule, unless there are unavoidable barriers (for example, the vaccine used for the first dose is not available). All varicella-containing vaccines authorized for use in Canada contain the Oka strain of live attenuated varicella virus. Refer to Principles of vaccine interchangeability in Part 1 for additional information about interchangeability of varicella vaccines.

Concurrent administration of vaccines

Varicella-containing vaccines may be administered concurrently with, or any time before or after, non-live vaccines, live oral vaccines, and live intranasal influenza vaccine (LAIV).

Varicella-containing vaccines may be administered concurrently with other routinely provided live parenteral vaccines. If not given concurrently, a minimum interval of 4 weeks is recommended between administration of varicella-containing and other live parenteral vaccines. This recommendation is to address the risk of interference from the vaccine given first on the vaccine given later.

Different injection sites and separate needles and syringes must be used for concurrent parenteral injections. Refer to Timing of vaccine administration in Part 1 for additional information about concurrent administration of varicella vaccine with other vaccines.

Storage and handling of immunizing agents

Refer to Storage and handling of immunizing agents in Part 1 for storage and handling recommendations for varicella vaccines.

Safety and adverse events

Common and local adverse events

Univalent varicella vaccine

Reactions to univalent varicella vaccine are generally mild and include injection site pain, swelling and redness in 10% to 20% of recipients. A low-grade fever has been documented in 10% to 15% of vaccine recipients. A varicella-like rash occurs at the injection site or is generalized in 3% to 5% of vaccine recipients after the first dose. The rash usually appears within 5 to 26 days after immunization. As varicella-like rashes that occur within the first 2 weeks after immunization may be caused by wild-type virus (varicella virus circulating in the community), health care providers should obtain specimens from the vaccine recipient to determine whether or not the rash is due to a natural varicella infection or to the vaccine-derived strain.

The safety profile of a 2 dose regimen is comparable to that of a single dose with slightly higher incidence of injection site reactions observed within 3 days after vaccination (up to 26%) and slightly lower incidence of fever (up to 4%) and varicella-like rash (1%) after dose 2 compared to dose 1.

Measles-Mumps-Rubella-Varicella vaccine

Pain and redness at the injection site or fever less than 39°C occur in 10% or more of vaccine recipients. Rash, including measles-like, rubella-like and varicella-like rash, as well as swelling at the injection site and fever greater than 39°C, occur in 1% to less than 10% of vaccine recipients. As varicella-like rashes that occur within the first 2 weeks after immunization may be caused by wild-type virus (varicella virus circulating in the community), health care providers should obtain specimens from the vaccine recipient to determine whether the rash is due to a natural varicella infection or to the vaccine-derived strain.

Varicella zoster immunoglobulin

Reactions to VarIg are rare. The most frequent treatment related adverse events are pain at the injection site (17%), headache (7%), and rash (5%).

Rubella-containing vaccines

Acute transient arthritis or arthralgia may occur 1 to 3 weeks after immunization with rubella-containing vaccine, such as MMRV. It lasts for about 1 to 3 weeks, and rarely recurs. It is more common in post-pubertal females, an age group for whom MMRV is not indicated. There is no evidence of increased risk of new onset chronic arthropathies.

Less common and serious or severe adverse events

Serious adverse events are rare following immunization and, in most cases, data are insufficient to determine a causal association. Anaphylaxis following vaccination with varicella-containing vaccine may occur but is very rare.

Univalent varicella vaccine

Most reported serious adverse events have not been proven to be caused by the vaccine, with the exception of rare events linked to the varicella vaccine strain among immunocompromised individuals or those with other serious medical conditions.

Measles-Mumps-Rubella-Varicella vaccine

Immune Thrombocytopenic Purpura (ITP)

Rarely, ITP occurs within 6 weeks after immunization with MMRV vaccine. In most children, post-immunization thrombocytopenia resolves within 3 months without serious complications. In individuals who experienced ITP with the first dose of MMRV vaccine, serologic status may be evaluated to determine whether an additional dose of vaccine is needed for protection. The potential risk to benefit ratio should be carefully evaluated before considering vaccination in such cases.

Encephalitis

Encephalitis has been reported in association with administration of measles vaccine in approximately 1 per million doses distributed in North America, which is much lower than the incidence observed with natural measles disease (1 per 1,000 cases).

Febrile seizures

Between the ages of 12 to 23 months, when the first dose of vaccine for measles and varicella is administered as the combined MMRV vaccine, there is a higher risk of fever and febrile seizures in the 7 to 10 days after vaccination when compared to separate administration of MMR and varicella vaccine at the same visit. For additional information about febrile seizures following the administration of MMRV vaccine, refer to Measles vaccine.

Varicella zoster immunoglobulin

There is a remote risk of an anaphylactic reaction to VarIg in individuals with hypersensitivity to blood products.

Other reported adverse events and conditions

Herpes zoster

HZ has been reported after varicella immunization. The risk of developing HZ is 4-fold to 12-fold lower in vaccinated as compared with unvaccinated children under 10 years of age who have had wild-type varicella. Severity of HZ has also shown to be reduced in vaccinated children compared to children with a history of wild-type VZV infection. The risk of HZ after vaccination with MMRV vaccine is unknown.

Transmission of vaccine virus

Transmission of vaccine strain virus from a healthy vaccine recipient is very rare. There have been few documented cases, all associated with a rash in the vaccine recipient.

Guidance on Reporting Adverse Events Following Immunization

Vaccine providers are asked to report the following AEFI in particular, through local public health officials:

Refer to Reporting adverse events following immunization (AEFI) in Canada and Adverse events following immunization in Part 2 for additional information about AEFI reporting.

Contraindications and precautions

Varicella-containing vaccines and VarIg are contraindicated in persons with a history of anaphylaxis after previous administration of the product and in persons with proven immediate or anaphylactic hypersensitivity to any component of the product, with the exception of egg allergy for MMRV vaccine. Refer to Contents of immunizing agents authorized for use in Canada in Part 1 for lists of vaccines and passive immunizing agents authorized in Canada and their contents.

In situations of suspected hypersensitivity or non-anaphylactic allergy to vaccine components, investigation is indicated which may involve immunization in a controlled setting. Consultation with an allergist is advised.

Although the measles and mumps components of MMRV vaccine are produced in chick embryo cell culture and may contain traces of residual egg and chicken protein, the trace amount of egg or chicken protein in the vaccine appears to be insufficient to cause an allergic reaction in egg-allergic individuals. Skin testing is not recommended prior to vaccination, as it does not predict reaction to the vaccine. MMRV vaccine can be administered in the routine manner to people who have a history of anaphylactic hypersensitivity to hens' eggs. Prior egg ingestion is not a prerequisite for immunization with egg protein-containing vaccine. For all vaccines, immunization should always be performed by personnel with the capability and facilities to manage adverse events post-vaccination. Refer to Contraindications and precautions in Part 2 for additional information.

Children with a known or suspected family history of congenital or hereditary immunodeficiency that is a contraindication to vaccination with live vaccine should not receive live vaccines unless their immune competence has been established.

MMRV vaccine is contraindicated in persons with impaired immune function, including primary or secondary immunodeficiency disorders. Vaccination with univalent varicella vaccine may be considered in select disorders. Refer to immunocompromised persons.

Varicella-containing vaccines are contraindicated during pregnancy because of theoretical risk to the fetus. Refer to pregnancy and breastfeeding.

Varicella-containing vaccines are contraindicated in individuals with active, untreated tuberculosis as a precautionary measure. Although tuberculosis may be exacerbated by natural measles infection, there is no evidence that measles-containing or varicella-containing vaccines have such an effect. Nonetheless, anti-tuberculous therapy for active TB disease is advisable before administering varicella-containing vaccines and it may be prudent to avoid live viral vaccines in those with active TB disease until treatment is underway. Consultation with an expert in infectious diseases is recommended.

A history of febrile seizures or a family history of seizures is not a contraindication for the use of MMRV vaccine.

Administration of varicella-containing vaccine should be postponed in persons with severe acute illness. Following measles infection, immunization with varicella-containing vaccine should be delayed by at least 4 weeks, and ideally 6 weeks, if feasible. Persons with a minor acute illness, with or without fever, may be vaccinated.

Following MMRV vaccine, transmission of measles, mumps and rubella vaccine viruses from vaccine recipients to susceptible contacts has not been documented, and transmission of varicella vaccine virus may occur very rarely between healthy vaccine recipients who develop a varicella-like rash and their susceptible contacts.

It is recommended to avoid the use of salicylates for 6 weeks after immunization with varicella-containing vaccine. Refer to drug-drug interactions.

Persons with specific immunoglobulin A (IgA) deficiency have increased potential for developing antibodies to IgA after receipt of blood products including VarIg and may be at risk for anaphylactic reactions to subsequent administration of blood products containing IgA, such as VarIg.

Refer to Contraindications and precautions in Part 2 for additional information.

Drug-drug interactions

Systemic antiviral therapy

Systemic antiviral therapy (such as acyclovir, valacyclovir, famciclovir) should be avoided in the peri-immunization period, as it may affect the reproduction of the vaccine virus and consequently may reduce the efficacy of varicella-containing vaccine. On the basis of expert opinion, it is recommended that people taking long-term antiviral therapy should discontinue these drugs, if possible, from at least 24 hours before administration of varicella-containing vaccine and should not restart antiviral therapy until 14 days after vaccine administration.

Tuberculin skin testing or Interferon Gamma Release Assay

The measles component in MMRV vaccine can temporarily suppress tuberculin reactivity, resulting in false-negative results. The effect of other live virus vaccines, such as univalent varicella vaccine on tuberculin reactivity is unknown. Until data are available, if tuberculin skin testing or an IGRA is required, it should be done on the same day as immunization or delayed for at least 4 weeks after varicella vaccination. Vaccination with a varicella-containing vaccine may take place at any time after tuberculin skin testing has been administered.

Salicylate therapy

Manufacturers of varicella-containing vaccines recommend avoidance of salicylate therapy (medications derived from salicylic acid, such as ASA) for 6 weeks after varicella immunization because of an association between wild-type varicella, salicylate therapy and Reye's syndrome. Health care providers should weigh the theoretical risks associated with varicella vaccine against the known risks associated with wild-type varicella infection. Because adverse events have not been reported with the use of salicylates after varicella immunization, people with conditions requiring chronic salicylate therapy should be considered for immunization, with close subsequent monitoring.

Human immunoglobulin or other blood products

Passive immunization with human Ig or receipt of most other blood products can interfere with the immune response to varicella-containing vaccine. These vaccines should be given at least 14 days prior to administration of an Ig preparation or other blood product or delayed until the antibodies in the Ig preparation or other blood product have degraded. If the interval between administration of vaccine and subsequent administration of an Ig preparation or other blood product is less than 14 days, or if the vaccine is administered before the antibody has degraded, the vaccine dose should be repeated after the recommended interval. The recommended interval between administration of an Ig preparation or other blood product and subsequent immunization with a varicella-containing vaccine varies, depending on the Ig preparation or blood product. RSV monoclonal antibodies (RSVmAb), nirsevimab or palivizumab and washed red blood cell transfusion do not interfere with the antibody response to varicella-containing vaccines. Refer to Blood products, human immunoglobulin and timing of immunization in Part 1 for additional information.

Other considerations

Surveillance

Virus identification from clinical specimens (for example, vesicle scraping) by laboratory methods to differentiate wild-type from vaccine-derived VZV should be considered when:

Polymerase chain reaction testing to differentiate vaccine-derived from wild type varicella virus can be performed by the National Microbiology Laboratory in Winnipeg.

As wild type varicella disease decreases with vaccination, laboratory confirmation of suspected varicella cases will become more and more important. Moreover, enhanced surveillance for varicella cases is necessary to ensure that the current immunization programs do not transfer the burden of illness into older age groups (for example, young adults of reproductive age) who are at risk of more severe disease.

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