Loading...
For both bivalent (Cervarix) and quadrivalent (Gardasil) human papillomavirus (HPV) vaccines, three-dose regimens impede ease of administration and raise cost. Investigators for an ongoing study of bivalent (HPV-16/18) vaccination in Costa Rican women (vaccine supplied by the manufacturer) evaluated whether one or two immunizations provide adequate protection against persistent HPV-16 or -18 infection (defined as infection that persisted for ≥10 months after the last vaccine dose).
Of 7153 evaluable women who were randomized to receive HPV or control vaccine, 5967 received three doses, 802 received two doses, and 384 received one dose. Among women who received all three doses, 4.4% of controls and 0.8% of HPV vaccine recipients exhibited persistent HPV-16/18 infection, corresponding to 81% vaccine efficacy. Vaccine efficacy was just as good in women who received fewer doses: 84% among women who received two doses (4.5% vs. 0.7% with persistent infection), and 100% among women who received one dose (5.3% vs. 0.0%).
Kreimer AR 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 Oct 5; 103:1444.
Comment
HPV vaccination could prevent most cervical cancers worldwide; however, coverage has been limited by low uptake in some countries (including the U.S.), failure to complete the three-dose series, and high cost. Evidence that immunization is effective when only one or two doses are administered could facilitate implementation of HPV vaccine programs, especially in regions where such need is greatest. Clinicians in developed countries can be reassured that even girls and women who do not complete the standard HPV-16/18 vaccination regimen receive considerable protection.