Direct benefit of vaccinating boys along with girls against oncogenic human papillomavirus: bayesian evidence synthesis

Abstract

Objective: To assess the reduction in the vaccine preventable burden of cancer in men if boys are vaccinated along with girls against oncogenic human papillomavirus (HPV).

Design: Bayesian evidence synthesis approach used to evaluate the impact of vaccination against HPV types 16 and 18 on the burden of anal, penile, and oropharyngeal carcinomas among heterosexual men and men who have sex with men. The reduced transmission of vaccine-type HPV from vaccination of girls was assumed to lower the risk of HPV associated cancer in all men but not to affect the excess risk of HPV associated cancers among men who have sex with men.

Setting: General population in the Netherlands.

Intervention: Inclusion of boys aged 12 into HPV vaccination programmes.

Main outcome measures: Quality adjusted life years (QALYs) and numbers needed to vaccinate.

Results: Before HPV vaccination, 14.9 (95% credible interval 12.2 to 18.1) QALYs per thousand men were lost to vaccine preventable cancers associated with HPV in the Netherlands. This burden would be reduced by 37% (28% to 48%) if the vaccine uptake among girls remains at the current level of 60%. To prevent one additional case of cancer among men, 795 boys (660 to 987) would need to be vaccinated; with tumour specific numbers for anal, penile, and oropharyngeal cancer of 2162, 3486, and 1975, respectively. The burden of HPV related cancer in men would be reduced by 66% (53% to 805) if vaccine uptake among girls increases to 90%. In that case, 1735 boys (1240 to 2900) would need to be vaccinated to prevent an additional case; with tumour specific numbers for anal, penile, and oropharyngeal cancer of 2593, 29107, and 6484, respectively.

Conclusions: Men will benefit indirectly from vaccination of girls but remain at risk of cancers associated with HPV. The incremental benefit of vaccinating boys when vaccine uptake among girls is high is driven by the prevention of anal carcinomas, which underscores the relevance of HPV prevention efforts for men who have sex with men.

Fig 1 Clustering of HPV related tumours in men who have sex with men. Number of men who have sex with men in population is represented by bar width. Herd immunity from vaccination of girls (area of white rectangle) is assumed not to affect number of cases of cancer attributable to male homosexuality (hatched area). Population attributable fraction is hatched area relative to total area

Fig 2 Lifetime risk of infection with HPV 16 or HPV 18 among heterosexual men relative to scenario without vaccination as function of vaccine coverage of girls. Box plots show variation from uncertainty about type specific parameters in HPV transmission model fitted to HPV infections in the Netherlands

Fig 3 Burden of HPV associated cancers in men in the Netherlands in relation to vaccine coverage of girls, overall and separately for carcinomas of oropharynx, anus, and penis. White bars (posterior median plus 1 SD) denote QALYs lost to all HPV types, whereas coloured bars denote estimated burden from vaccine preventable HPV types 16 and 18