[Articles] Human papillomavirus (HPV) type 16 and type 18 antibody concentrations after a single dose of bivalent HPV vaccine in girls aged 9–14 years compared with three doses of quadrivalent HPV vaccine in women aged 18–25 years in Costa Rica (PRIMAVERA): a non-randomised, open-label, immunobridging, non-inferiority trial

Non-inferior antibody responses for the single-dose bivalent HPV vaccine were seen for HPV-18 but not HPV-16, which would be insufficient evidence to motivate regulatory change, even though seropositivity approached 100% in the follow-up phase and the observed antibody concentrations were similar to protective levels seen in previous trials. Trials that directly evaluate protection afforded by single-dose HPV vaccination against persistent HPV infection will definitively address the level of protection afforded by single-dose HPV vaccination.