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Title: Cross-protection of the Bivalent Human Papillomavirus (HPV) Vaccine Against Variants of Genetically Related High-Risk HPV Infections.
Authors: Harari A,  Chen Z,  Rodríguez AC,  Hildesheim A,  Porras C,  Herrero R,  Wacholder S,  Panagiotou OA,  Befano B,  Burk RD,  Schiffman M,  Costa Rica HPV Vaccine Trial Group,  Costa Rica HPV Vaccine Trial CVT group
Journal: J Infect Dis
Date: 2016 Mar 15
Branches: BB, CGB, IIB, MEB
PubMed ID: 26518044
PMC ID: PMC4760417
Abstract: BACKGROUND: Results from the Costa Rica Vaccine Trial (CVT) demonstrated partial cross-protection by the bivalent human papillomavirus (HPV) vaccine, which targets HPV-16 and HPV-18, against HPV-31, -33, and -45 infection and an increased incidence of HPV-51 infection. METHODS: A study nested within the CVT intention-to-treat cohort was designed to assess high-risk HPV variant lineage-specific vaccine efficacy (VE). The 2 main end points were (1) long-term incident infections persisting for ≥2 years and/or progression to high-grade squamous intraepithelial lesions (ie, cervical intraepithelial neoplasia grade 2/3 [CIN 2/3]) and (2) incident transient infections lasting for <2 years. For efficiency, incident infections due to HPV-16, -18, -31, -33, -35, -45, and -51 resulting in persistent infection and/or CIN 2/3 were matched (ratio, 1:2) to the more-frequent transient viral infections, by HPV type. Variant lineages were determined by sequencing the upstream regulatory region and/or E6 region. RESULTS: VEs against persistent or transient infections with HPV-16, -18, -33, -35, -45, and -51 did not differ significantly by variant lineage. As the possible exception, VEs against persistent infection and/or CIN 2/3 due to HPV-31 A/B and HPV-31C variants were -7.1% (95% confidence interval [CI], -33.9% to 0%) and 86.4% (95% CI, 65.1%-97.1%), respectively (P = .02 for test of equal VE). No difference in VE was observed by variant among transient HPV-31 infections (P = .68). CONCLUSIONS: Overall, sequence variation at the variant level does not appear to explain partial cross-protection by the bivalent HPV vaccine.