This research is of special note because it provides evidence that two doses of the HPV 16/18 vaccine, and possibly even one dose, instead of the currently recommended three doses, may be sufficient to protect against cervical HPV 16/18 infection in the short term.
The authors evaluated the vaccine efficacy of fewer than three doses of an HPV 16/18 vaccine using data from the Costa Rica Vaccine Trial. Women were randomly assigned to receive three doses of the HPV 16/18 vaccine or a control vaccine and were followed for incident HPV 16 or HPV 18 infection that persisted in visits that were 10 or more months apart (median follow-up = 4.2 years). A total of 5,967 women received three vaccine doses (2,957 HPV, 3,010 control), 802 received two doses (422 HPV, 380 control), and 384 received one dose (196 HPV, 188 control). Incident HPV 16 or HPV 18 infections that persisted for one year were unrelated to dosage of the control vaccine. Vaccine efficacy was 80.9% for three doses of the HPV vaccine (CI = 71.1%–87.7%; 25 and 133 events in the HPV and control arms, respectively), 84.1% for two doses (CI = 50.2%–96.3%; 3 and 17 events), and 100% for one dose (CI = 66.5%–100%; 0 and 10 events). 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. (Kreimer AR, Rodriguez AC, Hildesheim A, et al. Proof-of-principle evaluation of the efficacy of fewer than three doses of a bivalent HPV16/18 vaccine. J Natl Cancer Inst 2011;103:1444–1451)
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