Varicella Vaccination and Post‑Exposure Prophylaxis Guidelines (CDC)
Routine Vaccination Strategy
The CDC recommends that all individuals without documented immunity receive two doses of varicella vaccine; the first dose at 12‑15 months (0.5 mL subcutaneously) and the second dose at 4‑6 years (before school entry) or ≥3 months after the first dose if given earlier. The second dose remains valid even if administered >28 days but <3 months after the first dose. Two‑dose regimens achieve 98.3 % efficacy, compared with 94.4 % for a single dose, reducing breakthrough disease risk by ≈ 3.3‑fold. 1
For adolescents and adults ≥ 13 years, the CDC advises two 0.5‑mL doses given 4‑8 weeks apart subcutaneously for those lacking immunity. Only the single‑antigen varicella vaccine is licensed for this age group (MMRV is not approved). 2, 3
Priority groups that should be ensured immunity include health‑care personnel, household contacts of immunocompromised persons, teachers, daycare employees, college students, military personnel, inmates, and non‑pregnant women of child‑bearing age. 4, 5
Catch‑Up Vaccination
- Individuals who have received only one dose should be given a second dose. The minimum interval is 3 months for children < 12 years and 4 weeks for persons ≥ 13 years; the dose may be administered after any longer interval. 6
Post‑Exposure Prophylaxis (VariZIG)
VariZIG (varicella‑zoster immune globulin) should be administered as soon as possible and no later than 10 days after exposure (extended from the previous 96‑hour window). 7
Dosing: 125 IU per 10 kg body weight, up to a maximum of 625 IU (five vials); infants ≤ 2 kg receive a minimum of 62.5 IU. 7
High‑Risk Groups Requiring VariZIG
| Population | Indication for VariZIG |
|---|---|
| Immunocompromised patients without evidence of immunity (including those on steroids > 2 mg/kg or ≥20 mg/day prednisone) | Immediate administration within 10 days of exposure. |
| Pregnant women without immunity (varicella in the first two trimesters can cause congenital varicella syndrome) | Administration plus routine antenatal immunity screening; postpartum vaccination for non‑immune women. |
| Newborns & premature infants – (a) newborns whose mothers develop varicella 5 days before to 2 days after delivery; (b) premature infants ≥ 28 weeks gestation if mother lacks immunity; (c) all infants < 28 weeks gestation or ≤ 1,000 g at birth regardless of maternal immunity | Administration according to weight‑based dosing. |
- After receiving VariZIG, wait ≥ 5 months before giving varicella vaccine. 7
Monitoring and Antiviral Management
- Patients who receive VariZIG should be observed for 28 days post‑exposure (extended incubation period). Initiate antiviral therapy promptly if any varicella signs or symptoms develop. 7
Institutional and Population Requirements
Health‑care personnel must be vaccinated to protect immunocompromised patients and reduce transmission risk. 1, 2
Substantial exposure in health‑care settings is defined as sharing a room or having direct face‑to‑face contact with an infectious patient. 8
School and post‑secondary entry: all students must have two documented varicella vaccine doses or other proof of immunity; requirements apply to every grade level, including college. 1, 9, 6
Common Pitfalls (CDC Alerts)
- Do not delay VariZIG beyond 10 days; efficacy remains comparable when given up to this limit. 7
- Bone‑marrow transplant recipients should be treated as non‑immune regardless of prior history. 8
- Do not use MMRV vaccine for persons ≥ 13 years; only the single‑antigen varicella vaccine is licensed for this age group. 3, 6
- Ensure 28‑day monitoring for VariZIG recipients rather than the standard 21‑day period. 7
Varicella Vaccination Schedule and Recommendations (American Academy of Pediatrics)
Children (12 months – 12 years)
Primary Series
- The first dose of varicella vaccine (0.5 mL subcutaneously) should be administered at 12–15 months of age. 10
- The second dose should be given at 4–6 years of age (before kindergarten or first‑grade entry), with a minimum interval of 3 months from the first dose. 10
- If the second dose is inadvertently administered 28 days to 3 months after the first dose, the series is considered complete and the dose does not need to be repeated. 10
Vaccine Options for Children
- Either monovalent varicella vaccine (Varivax) or the MMRV combination vaccine (ProQuad) may be used for children aged 12 months through 12 years. 10
- When all vaccine components are indicated, combination vaccines are preferred to reduce the number of injections. 10
Adolescents and Adults (≥13 years)
Vaccine Selection
- For persons aged 13 years and older, only the single‑antigen varicella vaccine (Varivax) is licensed; the MMRV combination is not approved for this age group. 10
Dosing Interval
- The two doses for adolescents and adults should be administered subcutaneously, 0.5 mL each, separated by a minimum of 4 weeks (28 days). 10
Catch‑Up Vaccination
Children Who Received Only One Dose
- Administer the second dose at least 3 months after the first dose; any interval longer than 3 months is acceptable. 10
Adolescents and Adults Who Received Only One Dose
- Administer the second dose at least 4 weeks after the first dose; longer intervals are permissible. 10
Contraindications (Severe Immunocompromise)
- Advanced HIV infection with CD4 count < 200 cells/µL. 10
- Active chemotherapy for cancer. 10
- High‑dose corticosteroid therapy (≥ 2 mg/kg/day or ≥ 20 mg/day prednisone for ≥ 14 days). 10
Administration Guidance
- Do not restart the series if the interval between the two doses exceeds the recommended timeframe; simply give the second dose when the individual presents. 10
- Do not delay the second dose in children beyond the 4–6 year window unless a medical contraindication exists, as this timing provides optimal protection for school entry. 10
- Do not use MMRV vaccine in persons ≥13 years; only the single‑antigen varicella vaccine is approved for this age group. 10