Cervical cancer prevention could become dramatically more accessible worldwide as evidence mounts that adolescent girls may need only one HPV vaccination instead of the currently recommended two doses. This finding addresses a critical global health gap where cost, logistics, and compliance barriers have left millions unprotected against the virus responsible for most cervical cancers.
A randomized trial involving 20,330 girls aged 12-16 demonstrated that single doses of both bivalent and nonavalent HPV vaccines provided statistically equivalent protection against HPV types 16 and 18 compared to the standard two-dose regimen. Over four years of follow-up, the infection rate difference between single and double dosing was negligible—less than 0.25 infections per 100 participants for both vaccine formulations. The study used rigorous noninferiority design with a prespecified margin of 1.25 infections per 100 participants, meaning single-dose protection needed to be within this threshold to be considered equivalent.
This represents potentially transformative evidence for global vaccination policy, particularly in resource-limited settings where reaching girls twice proves logistically challenging. Previous observational studies hinted at single-dose efficacy, but this represents the largest randomized controlled evidence to date. However, important caveats remain: the four-year follow-up period, while substantial, cannot yet confirm lifelong protection equivalence. The trial also focused on younger adolescents whose immune systems may respond more robustly than older populations. Nevertheless, for policymakers weighing coverage expansion against dosing intensity, this evidence suggests that vaccinating twice as many girls with single doses could yield superior population-level protection than maintaining two-dose requirements with lower uptake rates.