One shot of HPV vaccine protects long-term against cervical cancer

Women should be safe from cancer-causing human papilloma virus (HPV) for at least 20 years and probably more after just one dose of vaccine instead of the usual two or three, according to a study that further demonstrates the long-term effectiveness of a single dose.

When first approved by the Food and Drug Administration nearly 20 years ago, vaccines against cancer-causing HPV were scheduled in three doses for adequate protection. But the cost and logistics of giving three shots, particularly in remote or underserved regions, can make it difficult to complete the full regimen.

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The new study pulled data from the ongoing Costa Rica HPV Vaccine Trial, which provided initial evidence that one dose of the bivalent HPV vaccine protected against HPV-16/18 infections. Researchers wanted to see how durable that protection was, because early on scientists observed that antibody responses from three vaccine doses were about four times higher than those from just one dose.

So, they examined data from 500 of the Costa Rica trial participants. These included a group who had received three vaccine doses and a separate group aged 18 to 25 who got a single dose. All had agreed to follow-up visits 11, 14, and 16 years after vaccination.  

The researchers gauged antibody levels against HPV-16 and HPV-18 at 11 and 16 years post-vaccination and reported in the Journal of the National Cancer Institute Monographs that antibody levels declined a bit over five years – with the three-dose levels declining faster. But HPV-16 and HPV-18 antibody seropositive rates from both dosing regimens "remained exceedingly high 16 years after vaccination." 

"Given the one-dose levels observed at 16 years, we project that women will have adequate antibody levels for much longer after vaccination with the bivalent HPV vaccine," the scientists reported. “Therefore, our study lends additional support to the World Health Organization recommendation of using a single-dose HPV vaccine schedule in immunization programs worldwide.”

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The current research was led by the Division of Cancer Epidemiology and Genetics, National Cancer Institute (NCI), with collaborators Ligia Pinto, Ph.D., and Troy Kemp, Ph.D., of the Frederick National Laboratory for Cancer Research where all antibody testing was done; Doug Lowy, M.D., of NCI; and scientists from both Agencia Costarricense de Investigaciones Biomédicas, in San José, Costa Rica, and Information Management Services in Maryland.