Inconclusive evidence for non-inferior immunogenicity of two- compared with three-dose HPV immunization schedules in preadolescent girls: A systematic review and meta-analysis.

The European Medicines Agency (EMA) recently approved two-dose immunization schedules for bivalent (HPV 16/18) and quadrivalent (HPV 6/11/16/18) human papillomavirus (HPV) vaccines in nine to fourteen and thirteen year-old-girls, respectively. Registration was based on trials comparing immunogenicity of two-dose schedules in girls 9-14 years to three-dose schedules in young women 15-26 years. We evaluate comparability of antibody levels between and within age groups and discuss potential implications for monitoring the effectiveness of HPV vaccination.