SAN FRANCISCO, CA—A high rate of seroconversion was observed in HIV-positive girls aged 9–13 years given the quadrivalent human papillomavirus (qHPV) vaccine by standard dosing, with lower peak geometric mean titers (GMT) compared to same-aged girls without HIV infection, according to a study presented at IDWeek 2013.

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In addition, lower responses were observed in those with HIV without viral load suppression. However, these were comparable to women 16–26 years of age, suggesting the vaccine does confer efficacy against HPV infection and disease, said Deborah Money, MD, of the University of British Columbia and Women’s Health Research Institute, Vancouver, BC, Canada.

The qHPV vaccine was approved for use in HIV-negative adolescents in 2006 and leads to high rates of seroconversion. However, to date, information on immune responses to qHPV in children and adolescents with HIV infection is limited—even though HIV-positive women have higher rates of HPV than HIV-negative women—prompting Dr. Money and colleagues to initiate a open-label, multicenter study of qHPV in this population.

The primary study objective was to evaluate the sero-responsiveness of HIV-positive girls and women to a qHPV vaccine. The study was launched in November 2008 at 11 Canadian sites and enrollment was completed in December 2012 with 407 participants. Included were HIV positive women 9 years of age or older.

Participants were given 3 doses of qHPV at 0, 2, and 6 months. At 7, 12, 18, and 24 months, antibody responses were evaluated using the Merck competitive Luminex immunoassay (cLIA) to HPV types 6, 11, 16, and 18.

Of the 407 participants, 27 girls aged 9–13 years were enrolled and completed the vaccine schedule per protocol. GMTs were calculated and results compared with those from same-aged girls in the 3-dose arm of a 2-dose/3-dose qHPV comparative trial in HIV-uninfected girls.

One girl was seropositive to HPV 18 at baseline, while all others were seronegative to all types in the quadrivalent vaccine (6, 11, 16, ad 18). Mean time since HIV diagnosis was 9 years with median (IQR) CD4 nadir of 470 (230–610) cells/µL. At baseline, median CD4 was 710 (554–940) cells/µL and 67% had a suppressed viral load.

At months 7 and 24, there was a statistically significant difference between girls who were HIV-positive compared with those who were HIV-negative for all HPV types; however, this difference was not observed when HIV-positive girls were compared with HIV-negative girls ages 16–26 years.

All of the HIV-positive girls seroconverted to all of the vaccine-containing serotypes post series, for a 100% response. No vaccine-related serious adverse events were reported.

Patients with suppressed viral load at baseline had an approximately 2-fold higher GMT for all four serotypes than those with detectable viral load. However, the analysis was insufficiently powered to confirm a statistically significant difference.

“Until an immune correlate of protection is defined in HIV and HIV-positive persons, understanding of the meaning of antibody levels remains limited,” Dr. Money concluded, adding that the role of booster dosing remains to be evaluated.