Impact of gender-neutral or girls-only vaccination against human papillomavirus—Results of a community-randomized clinical trial (I)

Abstract

Human papillomavirus (HPV) vaccine is efficacious but the real-life effectiveness of gender-neutral and girls-only vaccination strategies is unknown. We report a community-randomized trial on the protective effectiveness [(PE) = vaccine efficacy (VE) + herd effect (HE)] of the two strategies among females in virtually HPV vaccination naïve population. We randomized 33 Finnish communities into Arm A) gender-neutral vaccination with AS04-adjuvanted HPV16/18 vaccine (11 communities), Arm B) HPV vaccination of girls and hepatitis B-virus (HBV) vaccination of boys (11 communities) or Arm C) gender-neutral HBV vaccination (11 communities). All resident 39,420 females and 40,852 males born 1992-95 were invited in 2007–09. Virtually all (99%) 12- to 15-year-old participating males (11,662) and females (20,513) received three doses resulting in uniform 20–30% male and 50% female vaccination coverage by birth cohort. Four years later (2010–14) 11,396 cervicovaginal samples obtained from 18.5 year-old women were tested for HPV DNA, and prevalence of cervical HPV infections by trial arm and birth cohort was the main outcome measure. VEs against HPV16/18 varied between 89.2% and 95.2% across birth cohorts in arms A and B. The VEs against non-vaccine types consistent with cross-protection were highest in those born 1994–95 for HPV45 (VEA 82.8%; VEB 86.1%) and for HPV31 (VEA 77.6%, VEB 84.6%). The HEs in the non HPV-vaccinated were statistically significant in those born 1994–95 for HPV18 (HEA 51.0%; 95% CI 8.3–73.8, HEB 47.2%; 6.5–70.2) and for HPV31/33 in arm A (HEA 53.7%; 22.1–72.5). For HPV16 and 45 no significant herd effects were detected. PE estimates against HPV16/18 were similar by both strategies (PEA 58.1%; 45.1–69.4; PEB 55.7%; 42.9–66.6). PE estimates against HPV31/33 were higher by the gender-neutral vaccination (PEA 60.5%; 43.6–73.4; PEB 44.5%; 24.9–60.6). In conclusion, while gender-neutral strategy enhanced the effectiveness of HPV vaccination for cross-protected HPV types with low to moderate coverage, high coverage in males appears to be key to providing a substantial public health benefit also to unvaccinated females. Trial registration www.clinicaltrials.gov.com NCT000534638.