• Iacopo Baussano, Fulvio Lazzarato, Guglielmo Ronco, Matti Lehtinen, Joakim Dillner, and Silvia Franceschi.
• International Agency for Research on Cancer, Lyon, France.
• J. Infect. Dis. 2017 Aug 1; 216 (3): 336-344.

BackgroundHuman papillomavirus (HPV) vaccination is still not reaching many high-risk populations. HPV16/18 vaccines offer cross-protection against other types, for example, HPV45. Both direct vaccine efficacy and indirect herd protection contribute to vaccination effectiveness.MethodsWe used a dynamic transmission model, calibrated to cervical screening data from Italy, to estimate vaccination effectiveness against HPV16 and HPV45 infection, assuming for HPV45 either 95% or lower cross-protection.ResultsBasic reproductive number was smaller (2.1 vs 4.0) and hence vaccine effectiveness and herd protection stronger for HPV45 than for HPV16. The largest difference in the reduction of infection prevalence in women <35 years old was found at 70% coverage in girls-only vaccination programs (99% vs 83% for total protection for HPV45 and HPV16, respectively, mainly owing to stronger herd protection, ie, 37% vs 16%). In gender-neutral vaccination, the largest difference was at 40% coverage (herd protection, 54% vs 28% for HPV16 and HPV45, respectively). With ≥80% coverage, even 50% cross-protection would reduce HPV45 by ≥94%.ConclusionsThe characteristics of individual high-risk HPV types strongly influence herd protection and determine the level of coverage and cross-protection required to reduce or eliminate the infection through HPV vaccination. HPV16 infection and related cancers are the most difficult to eliminate.© The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.

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