Long-term Immunogenicity and Safety of the AS04-adjuvanted Human Papillomavirus-16/18 Vaccine in Four- to Six-year-old Girls: Three-year Follow-up of a Randomized Phase III Trial.

Background: The burden of human papillomavirus (HPV) diseases is high in Latin America. HPV vaccines licensed from 2006 onwards offer protection against most HPV-related cancers, especially when introduced into national immunization programs. Barriers to optimal vaccine uptake are, however, lowering the impact of adolescent HPV vaccination programs. Immunization of children might overcome these barriers and be a strategy of choice for some countries.
Methods: This multicenter phase III randomized, controlled, single-blind study (NCT01627561) was conducted in Colombia, Mexico and Panama to assess safety and immunogenicity of 2-dose vaccination with AS04-adjuvanted HPV-16/18 vaccine in girls 4-6 years of age. We report safety outcomes and anti-HPV-16/18 antibody titers measured by enzyme-linked immunosorbent assay in HPV-vaccinated girls that were followed over a 36-month period.
Results: Over 36 months (ie, 30 months after the second vaccine dose), among 74 girls included in the HPV group, 1 serious adverse event unrelated to vaccination has been reported. No withdrawal because of (serious) adverse events has been reported. At month 36, all girls in the per-protocol-cohort were still seropositive for anti-HPV-16 and anti-HPV-18 with geometric mean concentrations of 1680.6 and 536.4 enzyme-linked immunosorbent assay units/mL, respectively.
Conclusions: The AS04-adjuvanted HPV-16/18 vaccine administered according to a 2-dose schedule to girls 4-6 years of age induced a high and sustained immunologic response with an acceptable safety profile during the 30 months following vaccination.