Dr. Matti Lehtinen, presented for the first time results from a community-randomized trial which was launched in Finland by the national public health institute and conducted by the University of Tampere in 2007-2014 instead of a national girls-only vaccination program.

Using the bivalent HPV16/18 vaccine, this study aimed to identify the HPV vaccination strategy with the highest impact. Excluding the Helsinki metropolitan area, all Finnish communities with more than 35,000 inhabitants (and 50 kms apart from each other) were randomized in 11 communities to receive gender-neutral HPV vaccination (Arm A), 11 communities to receive girls-only HPV vaccination (Arm B) and 11 communities to receive hepatitis B-virus (HBV) vaccination (Arm C). All resident females and males born 1992-95 were invited to participate in 2007–09 (ages of 12 to 15 years).

A uniquely high basic reproduction number (the number of cases with infection resulting from one infectious case) of HPV type 16 precluded induction of significant herd effect (protection of unvaccinated) with either one of the two HPV vaccination strategies strategies (Arm A and B). However, for HPV types 18, 31, 33 and 35 the somewhat delayed herd effects (visualized among the unvaccinated women by birth cohorts 1992 to 1995) were associated with the gender-neutral HPV vaccination strategy (Arm A) with low (20%) male and moderate (47.5%) female vaccination coverage (figure 1). For the girls-only vaccination strategy (Arm B), herd effect was observed only for HPV18.

The combination of cross-protective vaccine efficacy against HPV31/33/35 in vaccinated women and the herd effect in unvaccinated women afforded by the gender-neutral vaccination strategy provided approximately 60% overall protection against HPV types 31/33/35 which is identical to the overall protection against the vaccine types HPV16/18.

In conclusion, against most high-risk HPV types, gender-neutral vaccination has a strong impact already when moderate cross-protection and vaccination coverage apply. Eradication and/or elimination from any defined population of high-risk HPV types with higher reproduction number such as HPV16, will require higher vaccination coverage.

Gender-neutral vaccination has a strong impact already when moderate cross-protection and vaccination coverage apply.

Each dot represents one community receiving gender-neutral HPV vaccination (n=11, Arm A). The diameter of each point is proportional to the population size and the colour corresponds to the prevalence of HPV18/31/33/35 in 2011-2014 in non-HPV16/18 vaccinated 18 year-old girls. The mean vaccination coverage by community: boys 20%, girls 48%. The figure shows a reduction in the HPV prevalence among unvaccinated girls by birth cohort (from 1992 to 1995). Adapted from [1].

Figure 1. Prevalence of HPV18/31/33/35 in 2011-2014 by birth cohort (1992-1995) among non-vaccinated 18 year-old finnish girls following earlier gender-neutral vaccination of the same birth-cohorts in 2007-2009

References
1. Lehtinen M, Söderlund-Strand A, Vänskä S, et al. Impact of gender-neutral or girls-only vaccination against human papillomavirus-Results of a community-randomized clinical trial (I). Int J Cancer. 2018;142(5):949-58. Available from: https://onlinelibrary.wiley.com/doi/10.1002/ijc.31119