What are the recommendations for varicella (chickenpox) vaccination in adults?

Varicella Vaccination in Adults

All adults without evidence of immunity to varicella should receive a 2-dose series of single-antigen varicella vaccine administered 4-8 weeks apart (minimum 4 weeks), with special priority given to healthcare personnel, household contacts of immunocompromised persons, teachers, childcare workers, college students, military personnel, nonpregnant women of childbearing age, and international travelers. 1, 2

Defining Evidence of Immunity

Before vaccination, determine if the adult has evidence of immunity, which includes any of the following 1, 2:

• Documentation of 2 doses of varicella vaccine at least 4 weeks apart 1
• U.S.-born before 1980 (EXCEPT healthcare personnel and pregnant women—birth before 1980 does NOT count as immunity for these groups) 1
• Provider-diagnosed or verified history of varicella disease 1
• Provider-diagnosed or verified history of herpes zoster 1
• Laboratory evidence of immunity or laboratory-confirmed disease 1

Critical caveat: For patients with low or negative titers, documented receipt of 2 doses of varicella vaccine supersedes subsequent serologic testing results—do not revaccinate based on low titers alone if vaccination is documented. 3

Standard Vaccination Protocol

Dosing Schedule

• Administer the first dose immediately at the current visit 2
• Administer the second dose 4-8 weeks after the first dose (minimum acceptable interval is 4 weeks) 1, 2
• Use only single-antigen varicella vaccine in adults—MMRV is not licensed for persons aged ≥13 years 4

Administration Details

• Route: Subcutaneous injection of 0.5 mL per dose 4
• Coordination with other live vaccines: Administer varicella vaccine either on the same day as other live vaccines or separated by at least 28 days 2

Priority Populations Requiring Vaccination

Special consideration and emphasis should be given to the following high-risk groups 1, 2:

• Healthcare personnel (including those caring for severely immunocompromised patients) 1, 2
• Household contacts of immunocompromised persons 1, 2
• Teachers and childcare employees 1, 2
• College students and military personnel 1, 2
• Residents and staff of institutional settings (including correctional institutions) 1, 2
• Nonpregnant women of childbearing age 1, 2
• International travelers 1, 2
• Adolescents and adults living in households with children 1, 2

Rationale: Adults have significantly increased risk of severe varicella complications compared to children, including higher rates of pneumonia, disseminated disease, and hospitalization. 4, 5, 6

Absolute Contraindications

Do not administer varicella vaccine to 2, 3:

• Pregnant women (assess immunity during prenatal care, but defer vaccination until after pregnancy completion) 1, 2
• Individuals with severe immunocompromising conditions 2, 3
• Those with history of severe anaphylactic reaction to vaccine components 2

Special Population Management

Pregnancy-Specific Protocol

• Assess all pregnant women for varicella immunity during prenatal care 1, 2
• If non-immune, administer the first dose upon completion or termination of pregnancy and before discharge from the healthcare facility 1, 2
• Administer the second dose 4-8 weeks after the first dose 1, 2
• Counsel women of childbearing age to avoid conception for 1 month after each vaccine dose 3

Immunocompromised Patients

For HIV-infected adults 2, 3:

• May receive vaccination if CD4 count ≥200 cells/μL 2, 3
• Administer 2 doses separated by 3 months (not the standard 4-8 weeks) 2, 3

For patients on or planning immunosuppressive therapy 3:

• Vaccinate ≥4 weeks before starting therapy when possible 3
• Wait at least 1 month after discontinuing high-dose corticosteroids before vaccinating 2
• Vaccination is contraindicated in highly immunocompromised patients 3

Post-Exposure Prophylaxis

For non-immune adults exposed to varicella 2, 3, 7:

• Administer varicella vaccine within 3 days of exposure for maximum effectiveness 2, 3
• Vaccination up to 5 days post-exposure may still provide benefit 2, 3
• Post-exposure vaccination prevents approximately 26% of cases and 31% of hospitalizations 7
• Protective efficacy after household exposure is approximately 65% in adults 5

Important note: When breakthrough illness occurs in vaccinated adults, it is invariably mild, with 100% efficacy in preventing severe disease. 5

Clinical Efficacy and Immunogenicity

Two-dose vaccination provides superior protection 8:

• Seroconversion occurs in approximately 79% of adolescents after one dose 3
• Two doses achieve 99.6% protective titers compared to 85.7% after one dose 3
• Primary vaccine failure (not secondary waning) is the main cause of breakthrough varicella, suggesting the importance of completing the 2-dose series without unnecessary delay 8

Antibody persistence considerations 5, 9:

• Antibodies remain detectable in approximately 80% of vaccinated adults after 1 year and 70% from 2-6 years post-vaccination 5
• Natural infection produces higher antibody levels than vaccination, but clinical protection remains excellent 9

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 1
• Do not delay the second dose beyond 8 weeks without reason, as primary vaccine failure is more common than secondary waning 8
• Do not revaccinate adults with documented 2-dose vaccination based solely on low titers—documented vaccination supersedes serologic testing 3
• Do not use MMRV vaccine in adults—only single-antigen varicella vaccine is licensed for persons ≥13 years 4
• Do not forget to vaccinate susceptible adults before discharge if identified during hospitalization 1