A single dose of the human papillomavirus vaccine is as effective as two or three doses for preventing cervical cancer in girls and women vaccinated at 15-19 years of age, based on data from a retrospective study of more than 100,000 girls and women.
The Centers for Disease Control and Prevention’s current recommendations include a two-dose vaccine schedule for the HPV vaccine for girls and boys younger than 15 years, and a three-dose schedule for girls and young women aged 16-26 years who had their first dose before turning 15.
However, rates of HPV vaccination in the United States fall short of those in other developed nations, and evidence supporting the protective value of a specific number of vaccine doses are mixed, wrote Cancer., of the University of Texas Medical Branch at Galveston, and colleagues. Fewer than three doses could have benefits, including easier logistics, lower costs, higher acceptance rates, and fewer side effects, they said. The study was published in
The researchers reviewed data from 66,541 girls and women aged 9-26 years who had received at least one dose of HPV vaccine (4vHPV) between Jan. 1, 2006, and June 30, 2015, and 66,541 matched unvaccinated controls. The primary outcomes were histologically confirmed preinvasive cervical disease and high-grade cytology.
Overall, the adjusted hazard ratios for histologically confirmed preinvasive cervical disease among patients vaccinated at the ages of 15-19 years with one, two, and three doses were similar, at 0.64, 0.72, and 0.66, respectively, compared with unvaccinated individuals.
The risk of high-grade cytology was significantly lower for girls and women who received three doses at age 15-19 years, compared with unvaccinated individuals, but no difference was seen in high-grade cytology between unvaccinated individuals and those who received one or two doses. In addition, the unadjusted rate of preinvasive cervical disease at 5 years was 2.65% for unvaccinated teens aged 15-19 years, compared with 1.62%, 1.99%, and 1.86% in the one-, two- and three-dose groups, respectively.The findings were limited by several factors, including the use of billing codes to determine outcomes and the inability to determine potential vaccination through multiple insurance carriers, and the inclusion only of privately insured patients from the claims database, the researchers noted.
However, the results support findings from previous studies and show a similar level of association between varying vaccine doses and preinvasive cervical lesions in the 15- to 19-year-old population, they said.
“Efforts should focus on not only the need to initiate the HPV vaccine but also the need for beginning and continuing cervical cancer screening among young women who are vaccinated at older ages (18 years and older),” they said.
In an editorial accompanying the study, Cancer. 2020 Feb 10. doi: 10.1002/cncr.32696). “Initial observational data from vaccination programs did not support equivalent one-dose protection against genital warts or cervical disease, but such data may have been confounded by potentially higher risk characteristics of women who only ever received one or two doses of an intended three-dose course i.e., women noncompliant with the vaccine program [amplified by the monitoring of outcomes among the initial catch-up populations of already infected women]) and by the inherent bias that prevalent infection/disease is more likely to become apparent coincidently with the earlier doses in a vaccine course,” they said. The study findings have implications for global goals to eliminate cervical cancer, the editorial authors noted., and , of the University of Melbourne, Australia, and the Karolinska Institutet, Stockholm, respectively, wrote that the study’s strengths included the large numbers of girls and women who received a single dose of the HPV vaccine, compared with previous studies, as well as the adjustments for histories of sexually transmitted infections and pregnancy (
“If one dose of an HPV vaccine were sufficient for effective protection, HPV vaccine implementation and scale-up would require less logistics (while being amenable to a periodic campaign approach), available doses could be extended further, and the overall cost would be lower,” they said.
The study was supported in part by the National Center for Advancing Translational Sciences of the National Institutes of Health, and by the Cancer Prevention Research Institute of Texas. The researchers had no financial conflicts to disclose.
Dr. Brotherton disclosed serving as an investigator for Seqirus and Merck; Dr. Sundström disclosed research funding for her institution from Merck and MSD Sweden.
SOURCE: Rodriguez AM et al. Cancer. 2020 Feb 10. doi: 10.1002/cncr.32700.