The Cervarix vaccine for human papillomavirus (HPV) may provide protection with just one or two doses, rather than the standard three, according to an analysis of data from the National Cancer Institute (NCI)-sponsored Costa Rica Vaccine Trial.

Women participating in the study were to receive either three doses of Cervarix—intended to protect against HPV 16 and HPV 18—or the control vaccine. However, 20% of the 7,466 enrollees ultimately received fewer than three doses due to pregnancy, referrals to colposcopy, or other factors.

After excluding women who had no follow-up or who were HPV16 or HPV18 DNA-positive at enrollment, Aimée R. Kreimer, PhD, of the NCI’s Division of Cancer Epidemiology and Genetics in Bethesda, Maryland, and colleagues found that 5,967 participants received three vaccine doses (2,957 HPV vaccine vs 3,010 control vaccine), 802 received two doses (422 HPV vs 380 control), and 384 received one dose (196 HPV vs 188 control).

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Over 4 years of follow-up, similar levels of protection against HPV 16 and HPV 18 were seen among women in the three different HPV vaccine dose groups.

With three-dose regimens for HPV vaccines being expensive and difficult to complete, confirming the finding that fewer doses can be effective could help make primary prevention of cervical cancer a reality, wrote the investigators in Journal of the National Cancer Institute.