Long-term immune response to yellow fever vaccination in HIV-infected individuals depends on HIV-RNA suppression status: Implications for vaccination schedule.

Background

In HIV-infected individuals the immune response over time to yellow fever vaccination (YFV) and the necessity for booster vaccination are not well understood.

Methods

We studied 247 participants of the Swiss HIV Cohort Study (SHCS) with a first YFV after HIV diagnosis and determined their immune responses at one, five, and ten years postvaccination (p.v.) by yellow fever plaque reduction neutralisation titres (PRNT) in stored blood samples. A PRNT of 1:≥10 was regarded as reactive and protective. Predictors of vaccination response were analysed with Poisson regression.

Results

At vaccination, 82% of the vaccinees were taking combination antiretroviral therapy (cART), 83% had suppressed HIV RNA levels (<400 copies/ml), and their median CD4 cell count was 536 cells/mm3. PRNT was reactive in 46% (95% CI 38%-53%) before, 95% (91%-98%) within one year, 86% (79%-92%) at five years, and 75% (62%-85%) at 10 years p.v. In those with suppressed plasma HIV RNA at YVF, the proportion with reactive PRNT remained high: 99% (95%-99.8%) within one year, 99% (92%-100%) at five years, and 100% (86%-100%) at ten years.

Conclusions

HIV-infected patients' long-term immune response up to ten years to YFV is primarily dependent on the control of HIV replication at the time of vaccination. For those on successful cART, immune response up to ten years is comparable to that of non-HIV-infected adults. We recommend a single YFV booster after ten years for patients vaccinated on successful cART, while those vaccinated with uncontrolled HIV RNA may need an early booster.