Are 3 Doses Necessary for the HPV Vaccine?

According to an analysis from 2 randomized trials, 1 or 2 doses of the bivalent human papillomavirus (HPV) vaccine appeared to be as effective as the typical 3-dose regiment in protecting from cervical HPV type 16/18 infections.

“The main aim of the study was to ascertain HPV-16/18 vaccine efficacy in both full and naive cohorts and to explore protection conferred against non-vaccine HPV types, by number of doses received,” explained the study’s researchers.
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For the study, researchers randomly assigned women to receive either the HPV-16/18 vaccine or a control vaccine. After excluding women who were HPV-16/18 DNA-positive at baseline or who had less than 12 months of follow-up, researchers evaluated for 1-time detection of incident HPV-16/18 infections accumulated during the 4-year follow up phase.

Of the women, 22,327 received 3 doses, 1185 received 2 doses, and 543 were given 1 dose.

The study showed that the vaccine efficacy against incident HPV-16/18 infection was 77% for 3 doses, 76% for 2 doses, and 85.7% for 1 dose.

For incident HPV-31/33/45, vaccine efficacy was 59.7% for 3 doses, 37.7% for 2 doses, and 36.6% for 1 dose.

Vaccine efficacy against incident HPV-16/18 infection was 75.3% in women who received their second dose at 1 month and 82.6% for those that received their second dose after 6 months.

“Four years after vaccination of women aged 15–25 years, one and two doses of the HPV-16/18 vaccine seem to protect against cervical HPV-16/18 infections, similar to the protection provided by the three-dose schedule,” the researchers concluded.

“Two doses separated by 6 months additionally provided some cross-protection. These data argue for a direct assessment of one-dose efficacy of the HPV-16/18 vaccine.”

The complete study is published in the June issue of The Lancet Oncology.

-Michelle Canales Butcher

Reference:
Kreimer AR, Struyf F, Del Rosario-Raymundo M, et al. Efficacy of fewer than three doses of an HPV-16/18 AS04-adjuvanted vaccine: combined analysis of data from the Costa Rica Vaccine and PATRICIA trials. Lancet Oncol. 2015 June [epub ahead of print] doi: http://dx.doi.org/10.1016/S1470-2045(15)00047-9