What are the recommendations for varicella (chickenpox) vaccine administration in adults who have not had varicella or been previously vaccinated?

Varicella Vaccination in Adults

Primary Recommendation

All adults without evidence of immunity to varicella should receive two 0.5-mL doses of single-antigen varicella vaccine administered subcutaneously, 4-8 weeks apart. 1

Assessing Evidence of Immunity

Before vaccinating, determine if the adult has evidence of immunity, which includes any of the following 1:

• Documentation of 2 doses of varicella vaccine at least 4 weeks apart 1
• U.S.-born before 1980 (except for healthcare personnel and pregnant women, for whom birth before 1980 is NOT considered evidence of immunity) 1
• Healthcare provider-verified history of varicella or herpes zoster 1, 2
• Laboratory evidence of immunity or laboratory-confirmed disease 1

Vaccination Schedule and Administration

Dosing Regimen

• Two doses of 0.5 mL single-antigen varicella vaccine (Varivax) separated by 4-8 weeks 1
• Minimum interval: 4 weeks between doses for adults ≥13 years 1, 2
• If more than 8 weeks elapse after the first dose, administer the second dose without restarting the schedule 1
• Route: Subcutaneous injection 1, 2

Important Product Restriction

• Only single-antigen varicella vaccine (Varivax) may be used for persons ≥13 years 1, 2
• MMRV combination vaccine (ProQuad) is NOT licensed for adults and is only approved for children aged 12 months through 12 years 1, 2

Priority Populations Requiring Special Consideration

Adults at increased risk for exposure or transmission who lack evidence of immunity should receive priority vaccination 1, 2:

1. Healthcare personnel 1, 2
2. Household contacts of immunocompromised persons 1
3. Teachers and daycare employees 1, 2
4. College students, military personnel, and correctional facility inmates/staff 1, 2
5. Nonpregnant women of childbearing age 1, 2
6. International travelers 1, 2
7. Adolescents and adults living in households with children 1

Contraindications and Special Situations

Absolute Contraindications 1, 2

• Pregnancy (vaccine should be given postpartum before discharge) 1, 2
• Severe immunocompromising conditions (HIV with CD4 <200 cells/μL, active malignancy, immunosuppressive therapy) 1, 2
• History of anaphylactic reaction to neomycin or gelatin 2
• High-dose systemic corticosteroids (≥2 mg/kg/day prednisone or ≥20 mg/day for ≥14 days) 2

Important Clarifications

• Egg allergy is NOT a contraindication (varicella vaccine contains no egg protein) 2
• Contact dermatitis to neomycin is NOT a contraindication 2
• Having a pregnant household member is NOT a contraindication for vaccinating other family members 2

Special Population: HIV-Infected Adults

• Consider 2-dose series if CD4 count ≥200 cells/μL 1
• Contraindicated if CD4 count <200 cells/μL 1, 2

Pregnancy Management

• Assess all pregnant women for varicella immunity 1
• Birth before 1980 is NOT considered evidence of immunity for pregnant women due to potential severe consequences 1
• Administer first dose before discharge from healthcare facility after pregnancy completion or termination 1
• Second dose at 4-8 weeks (coinciding with postpartum visit) 1
• Counsel to avoid conception for 1 month after each dose 1

Post-Exposure Prophylaxis

If an unvaccinated adult without evidence of immunity is exposed to varicella 3:

• Administer vaccine within 3 days of exposure for >90% efficacy in preventing disease 3
• May still provide benefit up to 5 days post-exposure (approximately 70% efficacy in preventing disease, 100% efficacy in preventing severe disease) 3
• Avoid salicylates for 6 weeks post-vaccination due to Reye syndrome risk 3, 2

Alternative for High-Risk Patients

• For immunocompromised patients or pregnant women with contraindications to vaccination, administer varicella-zoster immune globulin (VZIG) within 96 hours of exposure 3, 4

Clinical Efficacy and Rationale

The two-dose regimen provides superior protection compared to single-dose vaccination 2:

• 98% efficacy against any varicella disease (vs. 94% with one dose) 2
• 100% efficacy against severe disease 2
• Recipients of 2 doses are 3.3-fold less likely to experience breakthrough varicella 2
• >99% of vaccinees achieve protective antibody levels after two doses (vs. 76-85% after one dose) 2

Common Pitfalls to Avoid

1. Do not use MMRV vaccine in adults - it is not licensed for persons ≥13 years 1, 2
2. Do not accept birth before 1980 as evidence of immunity for healthcare workers or pregnant women 1
3. Do not delay vaccination in adults who are sexually active or have had prior exposures - they should still receive the full two-dose series 2
4. Do not administer vaccine for 3-11 months after receiving blood products or immune globulin due to antibody interference 3
5. Do not wait for corticosteroid therapy to be discontinued - wait at least 1 month after discontinuation before vaccinating 2