For this study (HPV-023), participants from Brazil were invited to continue follow-up. 437 women from five centers participated in this 36-month long-term follow-up for 113 months (9.4 years). The aim of the study was to evaluate efficacy against HPV-16/18 infection and associated cyto-histopathological abnormalities, persistence of immunogenicity, and safety of the vaccine. During HPV-023, anti-HPV-16/18 antibodies were measured annually by enzyme-linked immunosorbent assay (ELISA) and pseudovirion-based neutralisation assay (PBNA). Cervical samples were tested for HPV DNA every 6 months, and cyto-pathological examinations were performed annually.
Efficacy against HPV-16/18 infections
During HPV-023, no new HPV-16/18-associated infections or cyto-histopathological abnormalities occurred in the vaccine group. In particular, VE against HPV-16/18 incident infection was 100%. VE was 95.6% against incident infection over 9.4 years. Looking at secondary endpoints, the data showed no cases of either 6- or 12-month HPV-16/18 persistent infection in the vaccine group, versus four cases and one case, respectively, in the placebo group during the 26-months follow-up.
Efficacy against cyto-histopathological abnormalities
VE against cyto-histopathological abnormalities was another secondary endpoint of the study. VE was 97.1% against atypical squamous cells of undetermined significance (ASC-US), 95% against low-grade squamous intraepithelial lesion (LISL), and 100% against cervical intraepithelial neoplasia grade 1 (CIN1+) and grade 2 (CIN2+) associated with HPV-16/18.
All vaccines remained seropositive to HPV-16/18, with antibody titers remaining several folds above natural infection
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