What is the recommended vaccination schedule for varicella in non-immune patients?

Varicella Vaccination for Non-Immune Adults

All non-immune adults should receive a 2-dose series of varicella vaccine administered 4-8 weeks apart, with a minimum acceptable interval of 4 weeks between doses. 1

Defining Non-Immunity

Before vaccination, you must establish that the patient lacks evidence of immunity. Evidence of immunity to varicella includes any of the following 1:

• Documentation of 2 doses of varicella vaccine at least 4 weeks apart
• U.S.-born before 1980 (except for healthcare personnel and pregnant women—these groups require vaccination regardless of birth year)
• Provider-diagnosed or verified history of varicella disease
• Provider-diagnosed or verified history of herpes zoster
• Laboratory evidence of immunity or laboratory-confirmed disease

If none of these criteria are met, the patient is considered non-immune and requires vaccination. 1

Standard Vaccination Schedule

Dose Timing

• First dose: Administer immediately at the current visit 2
• Second dose: Administer 4-8 weeks after the first dose 1
• Minimum acceptable interval: 4 weeks (28 days) between doses 1, 2

The 4-week minimum interval is based on immunological principles and clinical trial design for adults aged 13 years and older. 2, 3 While both 4-week and 8-week intervals are highly immunogenic (99% seroconversion), the 8-week interval produces higher antibody titers. 3

Vaccine Formulation

• Only single-antigen varicella vaccine (Varivax) may be used for persons ≥13 years 2
• MMRV combination vaccine is NOT approved for adults (only licensed for ages 12 months through 12 years) 2
• Each dose is 0.5 mL administered subcutaneously 2, 4

Priority Populations Requiring Vaccination

Special consideration for vaccination should be given to non-immune adults who 1, 2:

• Healthcare personnel (regardless of birth year before 1980)
• Household contacts of immunocompromised persons
• Teachers and childcare employees
• College students and military personnel
• Residents and staff of institutional settings (including correctional facilities)
• Nonpregnant women of childbearing age
• International travelers
• Adolescents and adults living in households with children

Absolute Contraindications

Do NOT administer varicella vaccine to 1, 2:

• Pregnant women (contraindicated; delay until after pregnancy)
• Severe immunocompromising conditions:
  • HIV infection with CD4 count <200 cells/μL
  • Congenital or acquired immunodeficiency
  • Leukemia, lymphoma, or generalized malignancy
  • Immunosuppressive therapy (including ≥2 mg/kg/day prednisone or ≥20 mg/day for ≥14 days)
  • Solid organ transplant recipients
• History of severe anaphylactic reaction to vaccine components (neomycin or gelatin) 2

Special Immunocompromised Considerations

• HIV-infected adults with CD4 count ≥200 cells/μL: May consider 2-dose series administered 3 months apart (not the standard 4-8 weeks) 1
• After discontinuing high-dose corticosteroids: Wait at least 1 month before vaccinating 2

Pregnancy-Specific Management

For pregnant women found to be non-immune 1:

1. Do NOT vaccinate during pregnancy (varicella vaccine is contraindicated)
2. Assess immunity during prenatal care
3. Administer first dose upon completion or termination of pregnancy, before discharge from healthcare facility
4. Administer second dose 4-8 weeks after the first dose
5. This applies regardless of whether the woman was born before 1980

Postexposure Prophylaxis

If a non-immune adult is exposed to varicella 2:

• Administer vaccine within 3 days of exposure (>90% effective in preventing disease)
• Vaccination up to 5 days post-exposure may still provide benefit (~70% effective in preventing disease, 100% effective in modifying severe disease)
• Avoid salicylates for 6 weeks after vaccination due to theoretical risk of Reye syndrome

Coordination with Other Live Vaccines

When administering varicella vaccine alongside other live vaccines (particularly MMR) 5:

• Either administer on the same day, OR
• Separate by at least 28 days
• Never administer live parenteral vaccines less than 28 days apart (except on the same day), as this may impair immune response

Clinical Efficacy Evidence

The superiority of 2-dose vaccination is well-established 6, 7:

• Seroconversion rates: 99% after 2 doses vs. 72-78% after 1 dose 3
• Incremental vaccine effectiveness: 63-81% additional protection with second dose 7
• Breakthrough infections: Recipients of 2 doses are 3.3-fold less likely to develop breakthrough varicella 2
• Antibody persistence: >99% maintain antibody at 1 year regardless of regimen, but geometric mean titers are significantly higher with 2 doses 8, 7

Common Pitfalls to Avoid

• Do not accept birth before 1980 as evidence of immunity for healthcare personnel or pregnant women—these groups require documented immunity or vaccination 1
• Do not use MMRV combination vaccine in adults—only single-antigen varicella vaccine is approved 2
• Do not restart the series if the interval between doses is prolonged—simply administer the second dose when the patient returns 2
• Do not administer varicella vaccine less than 28 days before or after another live parenteral vaccine unless given simultaneously 5
• Do not forget to counsel about avoiding pregnancy for at least 1 month after each vaccine dose in women of childbearing age 2