Two Doses - Instead of Three - Might Suffice for HPV Vaccine

A study in Costa Rica found that a fewer number of human papillomavirus vaccine shots than the standard three doses still conferred protection against incident HPV infections. If fewer shots were needed, it could help drive down program costs and lessen the logistical difficulties of administering three doses to adolescents in resource-poor countries, according to the National Cancer Institute (NCI), whose researchers led the study.

The trial randomly assigned thousands of women to receive three doses of the Cervarix vaccine, which protects against HPV types 16 and 18, or to a group receiving a three-shot control vaccine.

Researchers had intended to give all the women three shots total. By the study’s end, 5,967 women had received three shots; through various contingencies, 802 women got only two doses; and another 384 received only one. Median follow-up was 4.2 years, during which time the women were evaluated for incident HPV 16 or HPV 18 infection that persisted in visits that were 10 months or more apart. Cervarix vaccine efficacy was 80.9 percent for three doses, 84.1 percent for two doses, and 100 percent for one dose.

However, the study authors said it is still not known how long protection would last in patients receiving less than the recommended three doses.

“Four years after vaccination of women who appeared to be uninfected, this nonrandomized analysis suggests that two doses of the HPV 16/18 vaccine, and maybe even one dose, are as protective as three doses,” the authors reported.

“It may be that vaccinating more women, with fewer doses for each, will reduce cervical cancer incidence more than a standard three-dose program that vaccinates fewer women,” said Aimée R. Kreimer, PhD, lead author with NCI’s Division of Cancer Epidemiology and Genetics. “The main question will be whether the duration of protection from fewer doses is adequate.”

“If other studies confirm that fewer than three doses provide adequate protection against persistent cervical HPV 16 and 18 infection, we may be one step closer to prevention of cervical cancer, especially for women in resource-poor settings, where the need is greatest,” Kreimer said.

The full report, “Proof-of-Principle Evaluation of the Efficacy of Fewer than Three Doses of a Bivalent HPV 16/18 Vaccine,” was published in Journal of the National Cancer Institute (2011;103(19):1-8).

The Friends of AIDS Foundation is dedicated to enhancing the quality of life for HIV positive individuals and empowering people to make healthy choices to prevent the spread of the HIV virus. To learn more about The Friends of AIDS Foundation, please visit: http://www.friendsofaids.org.

TOGETHER WE REMAIN STRONG!