A major long-term trial has delivered the strongest evidence yet that a single jab provides two-dose protection.
Multidose human papillomavirus (HPV) vaccination is standard but with the recent downward trend in vaccination rates, should the focus be on just getting in one shot?
A new long-term trial of more than 20,000 girls and women found that one dose worked just as well as two doses at preventing HPV16 and HPV18 infections, with researchers suggesting single-dose vaccination could improve coverage without compromising efficacy.
Participants aged 12-16 years were randomly assigned to receive one or two doses of a bivalent HPV vaccine or a nonavalent HPV vaccine (1:1:1:1 ratio).
An additional 3000 unvaccinated participants aged 16-21 were enrolled in the survey portion of the trial for comparison.
For the bivalent vaccine, the difference between one and two doses was 0.13 fewer infections per 100 people. For the nonavalent vaccine, the difference was 0.21 more infections per 100 people.
Across all four trial groups, the vaccines were at least 97% effective and infection rates were superior to the survey-only group. No safety concerns were identified.
Participants were enrolled between 2017 and 2020 in the US and Costa Rica and followed up every six months for five years.
At each visit, both the trial and survey-only participants self-collected a cervicovaginal specimen, regardless of whether they reported that they had become sexually active yet. They also completed questionnaires about school, cigarette smoking, pubertal development and sexual history.
Six months after their first vaccine, the trial participants underwent randomisation again to either receive a second dose of their assigned vaccine or a DTaP shot (to maintain blinding).
The primary endpoint was HPV type 16 or 18 infection, the genotypes which account for around 77% of cervical cancer cases, but the nonavalent vaccine used covered seven carcinogenic HPV types, which account for around 95% of cervical cancers.
“The evidence from this trial supports the WHO alternative recommendation for single-dose HPV vaccination to achieve higher coverage while maintaining sufficiently high efficacy,” the paper read.
