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The multidose human papillomavirus (HPV) vaccination works but it is unclear if a single dose is sufficient for preventing infection. Kreimer AR et al (N Engl J Med 2025; 393:2421–2433, DOI: 10.1056/NEJMoa2506765) have published the results of a non-inferiority study, examining if one dose of an HPV vaccine was non-inferior to two doses in preventing HPV16 or HPV18 infection. Females aged 12–16 years were randomly assigned, in a 1:1:1:1 ratio, to receive one or two doses of a bivalent HPV vaccine or one or two doses of a nonavalent HPV vaccine. There were 20 330 participants who were randomised into the trial, and 3005 unvaccinated participants were enrolled in a survey. The non-inferiority analysis showed that one vaccine dose was non-inferior to two doses. The rate difference between one and two doses of the bivalent vaccine was −0.13 infections per 100 participants (95% CI −0.45 to 0.15; p<0.001 for non-inferiority). The difference between one and two doses of the nonavalent vaccine was 0.21 infections per 100 participants (95% CI −0.09 to 0.51; p<0.001 for non-inferiority). The vaccine effectiveness was at least 97% in each of the four trial groups. There were no safety concerns.