The HPV vaccine is highly effective against the cancer-causing types of human papillomavirus, but only half of teenagers and young adults have gotten all three of the doses recommended by the Centers for Disease Control and Prevention. Now a new study in women ages 18 to 26 suggests that one shot might be enough.
The analysis, in JAMA Open Network, included 1,620 women whose average age was 22. The prevalence of HPV infection was much higher among the 62 percent who were unvaccinated, but there was no significant difference between rates in those with a single dose versus those who had more.
For example, the rate of infection with types 6, 11, 16 or 18 (6 and 11 cause genital warts; 16 and 18 cause most cervical cancers) was 12.5 percent among the unvaccinated. It was 3.1 percent for those who had gotten all three shots, 5.1 percent for two shots, and 2.4 percent for one vaccination — a statistically insignificant difference.
The researchers had no information on the timing of the vaccinations, and the data depended on self-reports, which can be unreliable.
The lead author, Ashish A. Deshmukh, an assistant professor at the UTHealth School of Public Health in Houston, said that while these results are encouraging, three doses remain best for now. “Until we have clinical trials,” he said, “we should not rely on one dose.”