Single Dose of HPV Vaccine May Be Enough

A single dose of the human papillomavirus (HPV) vaccine produced antibodies against the disease and caused an immune system response 5 to 9 times stronger than in those infected with the disease naturally, researchers reported. Although single dose vaccination performed well in the study, levels of antibodies produced by women given only 1 dose of the vaccine were lower than in those given the standard 3 doses, calling into question the amount necessary to properly guard against infection. Researchers analyzed blood samples from women participating in The Costa Rica HPV16/18 Vaccine Trial, 78 of which received 1 dose, 192 who received 2 doses, and 120 who received all 3 doses of the vaccine, as well as 113 unvaccinated, previously HPV infected women. After 4 years of follow-up, every woman tested showed HPV antibodies in their blood samples. Levels of antibodies found in those who received 2 doses were “within range” of those who received the suggested 3 doses. Among those who received a single dose, “54% and 81% had HPV16 and HPV18 antibody levels at 48 months within the range observed among women who received all three doses,” researchers wrote. “The high efficacy after single dose suggests that long-term protection may not require the 5-fold higher titers induced by three doses of the vaccine,” they concluded. –Michael Potts Reference Safaeian M, Porras C, Pan Y Dreimer A, et al. Durable Antibody Responses Following One Dose of the Bivalent Human Papillomavirus L1 Virus-Like Particle Vaccine in the Costa Rica Vaccine Trial [published online ahead of print November 4, 2013. Cancer Prev Res . doi: 10.1158/1940-6207.CAPR-13-0203