Management of Individuals with Low or Negative Varicella Titer
For individuals with a low or negative Varicella (chickenpox) titer, immunization with 2 doses of varicella vaccine administered 4 weeks apart is strongly recommended. 1
Evidence of Immunity Assessment
- Evidence of immunity to varicella includes documentation of age-appropriate vaccination, laboratory evidence of immunity, laboratory confirmation of disease, or birth in the United States before 1980 (for non-healthcare workers who are not immunocompromised or pregnant) 1, 2
- Commercial ELISA tests are commonly used to detect varicella antibodies but may be less sensitive than other tests like fluorescent antibody to membrane antigen (FAMA) or latex agglutination (LA) tests 1
- Some individuals may have adequate cell-mediated immunity despite negative antibody titers, suggesting protection even with negative serologic results 3
Vaccination Recommendations Based on Immunity Status
For VZV-Seronegative Individuals:
- Administer 2 doses of varicella vaccine with an interval of 4 weeks between doses 1
- For adults aged 13 years and older, two doses of single-antigen varicella vaccine should be administered 4-8 weeks apart 2
- For children aged 12 months to 12 years, follow the routine two-dose vaccination schedule with the first dose at 12-15 months and second dose at 4-6 years 2
For Healthcare Personnel (HCP):
- Serologic screening before vaccination is cost-effective for HCP with negative or uncertain history of varicella 1
- HCP with low or negative titers should receive vaccination to prevent potential nosocomial transmission to high-risk patients 1
- Institutions may elect to test all HCP regardless of disease history, as a small proportion with positive history might still be susceptible 1
- Routine testing for varicella immunity after 2 doses of vaccine is not recommended for HCP management 1
Special Considerations
Immunocompromised Individuals:
- Live varicella vaccination is contraindicated in patients receiving immunosuppressive therapy or with significant protein-calorie malnutrition 1
- For patients on immunomodulators who are varicella antibody negative, consider vaccination during a treatment window if possible 1
- If vaccination is not possible due to ongoing immunosuppression, patients should be advised to avoid contact with people with active chickenpox or herpes zoster 1
- Post-exposure prophylaxis should be considered if exposed to active chickenpox or herpes zoster 1
Non-Responders to Initial Vaccination:
- Some individuals may remain seronegative after two doses of varicella vaccine (approximately 11.9% in one study) 4
- A third dose of vaccine may be considered for those who remain seronegative after two doses 4, 5
- Studies show that 7 out of 7 initially seronegative healthcare workers seroconverted after a third dose, though 3 produced low-avidity antibodies 4
Post-Exposure Management
- Varicella vaccine is effective when administered within 3 days of exposure, and possibly up to 5 days post-exposure, with effectiveness of approximately 70-90% in preventing varicella 2
- For high-risk individuals with contraindications to vaccination, varicella-zoster immunoglobulin (VariZIG) should be administered as soon as possible after exposure, but may be effective if given within 96 hours 2, 6
- Unvaccinated individuals exposed to varicella should receive post-exposure vaccination as soon as possible 1
Important Caveats
- Commercial ELISA tests may not detect vaccine-induced antibodies as effectively as they detect antibodies from natural infection 3
- Cell-mediated immunity plays a significant role in long-term protection against varicella, and absence of antibodies does not necessarily mean susceptibility 1, 3
- Documented receipt of 2 doses of varicella vaccine supersedes results of subsequent serologic testing 1
- Healthcare institutions should establish protocols for screening, vaccinating, and managing personnel after workplace exposures 1