Vaccination Recommendation for Immunocompetent Adult with Remote Varicella Exposure
Yes, vaccinate with 2 doses of varicella vaccine separated by at least 28 days, as this person lacks evidence of immunity and requires the standard two-dose regimen recommended for all susceptible individuals ≥13 years of age. 1
Evidence of Immunity Assessment
The exposure 17 years ago without subsequent disease does not constitute evidence of immunity. According to current guidelines, evidence of immunity requires one of the following 1:
- Documented 2 appropriately-timed doses of varicella vaccine 1
- Laboratory-confirmed varicella-zoster IgG positivity 1
- Healthcare provider-verified history of varicella or herpes zoster disease 1
A single exposure without documented infection or vaccination does not meet any of these criteria, leaving this individual susceptible and requiring vaccination 1.
Standard Two-Dose Vaccination Protocol
For immunocompetent persons ≥13 years of age without evidence of immunity 1:
- Administer two 0.5-mL doses of monovalent varicella vaccine 1
- Separate doses by at least 28 days (minimum interval based on clinical trial design) 1
- Use single-antigen varicella vaccine, not MMRV combination (MMRV is not licensed for this age group) 1
The two-dose regimen achieves 98% efficacy in preventing varicella over 10 years, compared to 94% for a single dose—representing a 3.4-fold lower breakthrough risk 2.
Why Two Doses Are Essential
The second dose is not optional—it provides critical additional protection 2:
- Among adolescents and adults receiving two doses 4-8 weeks apart, 83% remained completely protected after household exposure to varicella 2
- The 17% who developed breakthrough disease experienced only mild illness (median <50 lesions, none >75 lesions) 2
- Annual breakthrough rates after two doses range from 0-1.2% versus up to 2.3% after one dose 2
Critical Pitfall to Avoid
Do not rely on serologic testing to determine vaccination eligibility 1, 3:
- Commercial ELISA assays lack sensitivity to detect vaccine-induced antibodies in all cases, with false-negative rates up to 25-31% despite protective immunity 3
- The CDC explicitly states that persons lacking acceptable evidence of immunity should be vaccinated without serologic testing 1
- Post-vaccination serologic testing is also not recommended, as negative results do not indicate lack of protection due to cell-mediated immunity 3, 4
Special Considerations
If this person were planning immunosuppressive therapy, vaccination should occur ≥4 weeks before initiating treatment to allow optimal immune response and viral clearance 1. However, for routine vaccination in an immunocompetent adult, no special timing considerations apply beyond the 28-day interval between doses 1.
Healthcare workers in this situation require two documented doses regardless of birth year, as birth before 1980 is not considered evidence of immunity for personnel due to nosocomial transmission risk 5.