Assessment of herd effects among women and heterosexual men after girls‐only HPV16/18 vaccination in the Netherlands: A repeated cross‐sectional study

Abstract

Data on the impact of human papillomavirus (HPV) vaccination on the population HPV prevalence are largely obtained from women. We assessed the impact of the girls‐only HPV16/18 vaccination program in the Netherlands that started in 2009, on trends in HPV prevalence among women and heterosexual men, using data from the PASSYON study. In this cross‐sectional study, the HPV prevalence among 16‐ to 24‐year‐old visitors to sexually transmitted infection clinics was assessed in 2009, 2011, 2013, and 2015. We compared the genital postvaccination HPV prevalence with the prevaccination prevalence (2009) using Poisson GEE models. In total, we included 4,996 women and 1,901 heterosexual men. The percentage of women who reported to be vaccinated increased from 2.3% in 2009 to 37% in 2015. Among all women, the HPV16/18 prevalence decreased from 23% prevaccination to 15% in 2015 (adjusted prevalence ratio [aPR] 0.62, p trend < 0.01). Among heterosexual men, the HPV16/18 prevalence decreased from 17% prevaccination to 11% in 2015 (aPR 0.52, p trend < 0.01). Of the heterosexual men with a steady partner, HPV16/18 prevalence was lower among those whose steady partner had been vaccine‐eligible in the national immunization program (aPR 0.13). Among unvaccinated women, the HPV16/18 prevalence in 2015 was not different from prevaccination. The decreasing HPV16/18 prevalence among heterosexual men and the reduced HPV16/18 prevalence among heterosexual men with a vaccine‐eligible steady partner strongly suggests herd protection from girls‐only vaccination. Absence of notable herd effects among unvaccinated women 6 years postvaccination may be due to the moderate vaccine uptake among girls in the Netherlands.

Population Impact of Girls-Only Human Papillomavirus 16/18 Vaccination in The Netherlands: Cross-Protective and Second-Order Herd Effects

“…For women, this is partly explained by an increased proportion of vaccinated women over time who benefit from direct protection of HPV-16/18 vaccination. In a previous analysis with data up to 6 years postvaccination, we reported that heterosexual men already benefited indirectly from this through herd protection [ 10 ]. This finding is reiterated in the current analyses with data up to 8 years postvaccination.…”

“…For this updated analysis, we used data from the PASSYON (Papillomavirus Surveillance Among STI Clinic Youngsters in the Netherlands) study: a biennial cross-sectional survey to assess HPV prevalence among young visitors to SHCs [ 10 ]. In the Netherlands, SHCs offer sexually transmitted infection (STI) testing to those with increased risk, including individuals ≤24 years of age.…”

“…Due to funding restrictions from 2015 onward, SHCs became stricter in prioritizing individuals at high risk for STIs, which could have resulted in a study population at systematically increased risk for HPV infection starting from 2015 [ 14 ]. As we assumed we were unable to fully adjust for this by only including changes over time in the known variables [ 10 ], we adjusted for policy change by including a categorical variable indicating the policy change from 2015 onward.…”

“…Previously, we demonstrated herd effects for vaccine types HPV-16/18 among heterosexual men 6 years after introduction of girls-only HPV-16/18 vaccination in the Netherlands [ 10 ]. Herd effects among unvaccinated women were not yet observed within 6 years postvaccination, presumably due to the moderate vaccine uptake in the Netherlands.…”

Who Will Benefit From Expanding HPV Vaccination Programs to Boys?

“…This finding, counterintuitive at first sight, stems from the high burden of cervical cancer compared with other HPV-related cancers and from the notion that herd effects from vaccinating one sex are generally stronger in the opposite sex (10,31,33). The last also explains the strong impact of girls’ vaccination on vaccine-preventable HPV infections in heterosexual men (34,35).…”