Antibody responses to prophylactic quadrivalent human papillomavirus vaccine at 48 months among HIV-infected girls and boys ages 9-14 in Kenya, Africa

Objectives: HIV infected children remain at increased risk of HPV associated malignancies as they initiate sexual activity. Though they mount a vigorous immune response to the quadrivalent human papillomavirus (QHPV-6, -11,-16, and -18; Gardasil®) vaccine, durability of the immune response is uncertain. We assessed antibody responses to HPV 6, -11, -16 and -18 for up to 48 months following administration of quadrivalent human papillomavirus vaccine in HIV-infected girls and boys ages 9-14 years in Kenya.

Design: Of 178 girls and boys who had previously received three doses of the quadrivalent HPV vaccine, 176 enrolled into extended follow up for 4 years. HPV antibodies to -6, -11, -16 and -18 were measured at 24, 36 and 48 months after the first vaccine dose using the total immunoglobulin G immunoassay (IgG LIA). We evaluated the magnitude and trend in HPV vaccine response and the effect of plasma HIV-1 RNA on HPV vaccine response from month 24 to month 48 of follow up.

Results: At re-enrollment, 24 months after initial vaccination, median age of participants was 14 years (range 11-17); 167 (95%) were receiving antiretroviral therapy and 110 (66%) had plasma HIV RNA < 40 copies/mL. The rate of HPV seropositivity at 48 months was 83% for HPV-6; 80% for HPV-11; 90% for HPV-16; and 77% for HPV-18. There was a plateau in mean log10 HPV-specific antibody titer between month 24 and 48. The mean log10 HPV-type specific antibody titer for children with undetectable HIV viral load (<40) at the time of vaccination consistently remained higher for the 48 months of follow up compared to children with detectable viral load.

Conclusion: Children with HIV infection may retain long term antibody response following HPV immunization. Further work to define whether HIV-infected children are protected from HPV acquisition with low levels of HPV antibodies is needed.