In a prospective cohort study reported in The Lancet Oncology, Partha Basu, MD, and colleagues found that a single dose of quadrivalent human papillomavirus (HPV) vaccine given to girls in India provided 10-year protection equal to two or three doses against persistent infection with HPV types 16 and 18, the genotypes responsible for the majority of cases of cervical cancer.
Study Details
The multicenter study was originally a randomized trial comparing two vs three doses of quadrivalent vaccine in unmarried girls aged 10 to 18 years. As stated by the investigators, “In response to seven vaccine-unrelated deaths reported in another ongoing HPV vaccination demonstration program in the country, the Indian government issued a notification on April 8, 2010, to stop further recruitment and HPV vaccination in all clinical trials.”
The study was thus converted into a longitudinal prospective cohort study evaluating the efficacy of one, two, and three vaccine doses compared with age- and center-matched unvaccinated controls. Analysis of efficacy was adjusted for imbalance in the distribution of potential confounders between the unvaccinated and vaccinated cohorts. Participants were recruited between September 1, 2009, and April 8, 2010 (date of vaccination suspension). The primary outcome measure was protection against persistent HPV–16/18 infection.
A single dose of HPV vaccine provides similar protection against persistent infection from HPV-16 and HPV-18, the genotypes responsible for nearly 70% of cervical cancers, to that provided by two or three doses.— Partha Basu, MD, and colleagues
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Key Findings
Vaccinated participants were followed for a median of 9.0 years (interquartile range = 8.2–9.6 years). Analysis of evaluable participants included 2,135 women who had received a single vaccine dose, 1,452 who had received two doses, 1,460 who had received three doses, and 1,260 unvaccinated women.
Vaccine efficacy against persistent HPV–16/18 infection was 95.4% (95% confidence interval [CI] = 85.0%–99.9%) in the single-dose cohort, 93.1% (95% CI = 77.3%–99.8%) in the two-dose cohort (difference vs 1 dose = –2.0%, 95% CI = –20.2%–11.3%), and 93.3% (95% CI = 77.5%–99.7%) in the three-dose cohort (difference vs 1 dose = –1.9% (95% CI = –19.4%–12.4%).
Efficacy rates against persistent HPV-16, -18, -6, and -11 infections were 93.4% (95% CI = 81.1%–99.1%), 93.7% (95% CI = 79.8%–99.8%), and 90.3% (95% CI = 71.9%–98.5%), respectively. Efficacy rates against any persistent HPV infection were 35.4% (95% CI = 3.7%–56.0%), 36.7% (95% CI = 1.6%–57.9%), and 39.3% (95% CI = 6.8%–60.2%), respectively.
The investigators stated, “The fragile health systems of low-income and middle-income countries are inadequately prepared to face the formidable challenge of delivering two doses of the vaccine to adolescent girls. These countries will be further affected by the huge gap in supply and demand, as the global requirement of the vaccine is expected to rise to 120 million doses per year by 2030…. Adoption of a single-dose schedule for the HPV vaccine could potentially address many of the challenges by improving affordability, making the vaccination programs logistically simpler and more resilient, and helping to tide over the supply crisis.”
They concluded, “A single dose of HPV vaccine provides similar protection against persistent infection from HPV-16 and HPV-18, the genotypes responsible for nearly 70% of cervical cancers, to that provided by two or three doses.”
Dr. Basu, of the Early Detection, Prevention, and Infections Branch at the International Agency for Research on Cancer, Lyon, is the corresponding author for The Lancet Oncology article.
Disclosure: The study was funded by the Bill & Melinda Gates Foundation. For full disclosures of the study authors, visit thelancet.com.
