Varicella vaccine readings - HEALTH CANADA

Question 1

What is the efficacy of varicella vaccines in children?

Answer 1

The efficacy of varicella vaccines in children is estimated to be 94.4% following a single dose and 98.3% following a second dose.

Question 2

What are common reactions to varicella vaccine?

Answer 2

Reactions to univalent varicella vaccines include: pain, swelling and redness at the injection site in 10% to 20% of vaccine recipients; low grade fever in 10% to 15%; and a varicella-like rash in 3% to 5% of vaccine recipients after the first dose and 1% after the second dose.

Question 3

What type of reaction is more likely if the MMRV vaccine is given in children 12 to 23 months of age vs. just the MMR vaccine?

Answer 3

When the first dose is administered to children 12 to 23 months of age as 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 measles-mumps-rubella (MMR) and univalent varicella vaccine at the same visit.

Question 4

WHen should varicella vaccine be prioritized?

Answer 4

1. Non-pregnant women of childbearing age
2. Household contacts of immunocompromised individuals
3. Members of a household expecting a newborn
4. Health care workers
5. Adults who may be exposed occupationally to varicella (for example, people who work with young children)
6. Immigrants and refugees from tropical regions
7. People receiving chronic salicylate therapy (for example, acetylsalicylic acid [ASA])
8. People with cystic fibrosis
9. Susceptible adults exposed to a case of varicella

Question 5

Who is the MMRV vaccine recommended in?

Answer 5

• Univalent varicella or MMRV vaccine is recommended for routine immunization of healthy children aged 12 months to less than 13 years of age.
• Univalent varicella vaccine is recommended for susceptible adolescents (13 to less than 18 years of age) and susceptible adults (18 to less than 50 years of age).
• Univalent varicella vaccine may be considered for people with select immunodeficiency disorders.

Question 6

WHen should varicella vaccine be administered routinely in children?

Answer 6

2 doses of any varicella-containing (univalent varicella or MMRV) vaccine. The first dose of varicella-containing vaccine 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

Question 7

What about children 12 months to < 13 years?

Answer 7

Children aged 12 months to less than 13 years of age not immunized on the routine schedule: 2 doses of any varicella-containing vaccine

Question 8

What about for adolsecents and adults (18-50 years)

Answer 8

2 doses of univalent varicella vaccine

Question 9

How long should salicylates be avoided after varicella vaccination?

Answer 9

6 weeks!

Question 10

How is varicella transmitted?

Answer 10

• Airborne and direct contact with virus shed from skin lesions.

Question 11

How long is the incubation period?

Answer 11

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.

Question 12

Which groups are at increased risk of SEVERE varicella?

Answer 12

• Newborn infants
• neonates
• Susceptible pregnant women
• HIV patients
• ## Recipients of hematopoietic stem cell transplantation

Question 13

What are the symptoms?

Answer 13

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.

Question 14

What are the main complications of varicella?

Answer 14

• secondary bacterial skin infection
• soft tissue infections
• bacteremia
• pneumonia
• osteomyelitis
• Sepcti arthritis
• necrotizing fasciitis, toxic shock like syndrome, cerebella ataxia, stroke and ecephalitis.

Question 15

How much does varicella increases the risk of severe invasive group A streptococcal infection in previously health invasive group A strep.

Answer 15

40 to 60 fold

Question 16

What groups get chicken pox in countries without vaccination?

Answer 16

50% in children by age 5

Question 17

What is the estimated vaccine effectiveness 10 years following the receipt of 2 doses of univalent varicella vaccine?

Answer 17

98%

Question 18

What is the recommended interval between 2 doses of varicella vaccine?

Answer 18

3 months

Question 19

What should happen with adults 50 years of age and older FOUND to be serologically susceptible to varicella based on prevous lab testing?

Answer 19

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.

Question 20

Which individuals are considered immune to varicella?

Answer 20

Documented evidence of immunization with 2 doses of a varicella-containing vaccine
Laboratory evidence of immunity

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).

Question 21

When is a self-reported history or diagnosis of varicella or HZ by healthcare provider not considered an acceptable evidence of immunity?

Answer 21

healthy pregnant women with significant exposure to VZV (refer to significant exposures to VZV)
immunocompromised individuals
HCW who are newly hired into the Canadian health care system

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.

Question 22

When might post exposure immunization be necessary?

Answer 22

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

Continuous household contact (that is, living in the same dwelling) with a person with varicella
Being indoors for more than 1 hour with a person with varicella
Being in the same hospital room for more than 1 hour, or more than 15 minutes of face-to-face contact with a person with varicella
Touching the lesions or articles freshly soiled by discharges from vesicles of a person with active varicella

Question 23

What are significant exposure to VZV as a result of contact with a person with HZ?

Answer 23

Continuous household contact (that is, living in the same dwelling) with an immunocompromised person with HZ or a person with disseminated HZ prior to or within first 24 hours of antiviral treatment
Being indoors for more than 1 hour with an immunocompromised person with HZ or a person with disseminated HZ prior to or within first 24 hours of antiviral treatment
Being in the same hospital room for more than 1 hour, or more than 15 minutes of face-to-face contact with an immunocompromised person with HZ or a person with disseminated HZ prior to or within first 24 hours of antiviral treatment
Touching the lesions or articles freshly soiled by discharges from vesicles of a person with active HZ

Question 24

Which type of vaccine is best for post-exposure immunization?

Answer 24

• Univalent varicella vaccine

Question 25

When Varicella zoster immunoglobulin indicated?

Answer 25

The exposed person is susceptible to varicella. Refer to susceptibility and immunity.
There has been a significant exposure to a person with varicella or HZ. Refer to significant exposures to VZV.
The exposed person is at increased risk of severe varicella. Refer to persons at increased risk of severe varicella.
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.

Question 26

Should women who are pregnant get vaccinated with varicella vaccine?

Answer 26

NO!
Breast feeding - YES

Question 27

Can someone being treated with hydroxycholoroquine, sulfasalazine, or auranofin be vaccinated with varicella vaccine?

Answer 27

• YES - they are not considered immunosuppressive

Question 28

What about the conditions requiring chronic salicylate therapy?

Answer 28

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.

Question 29

What should we do with varicella susceptability and immunocompromised folks?

Answer 29

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.