HPV Vaccine: How High Vaccination Rates Benefit Unvaccinated Women

The vaccination against Human Papillomavirus (HPV) effectively protects against precancerous changes in the cervix and invasive cervical cancers. A population study from Sweden indicates that unvaccinated women also benefit from a broad vaccination strategy.

Registry Study Examined Indirect Vaccine Protection

A research team led by Eva Meglic from the Karolinska Institute in Stockholm investigated the indirect protective effect of the state-organized HPV vaccination program established in Sweden in 2012. They compared four birth cohorts of unvaccinated girls and women regarding the incidence of high-grade cervical intraepithelial neoplasia (CIN). Data from 857,168 women were analyzed.

The reference group consisted of women born between 1985 and 1988, with an HPV vaccination rate of only about 6%. Participants from the years 1989-1992 experienced an opportunistic vaccination program, while those born between 1993 and 1998 were eligible for catch-up vaccinations. The state-organized program aimed at girls aged 10 to 12 years finally benefitted those born in 1999 and 2000, achieving a vaccination rate of 72%.

Over time, a significant herd effect of the HPV immunization became evident, as reported by the study team. For neoplasia, the adjusted incidence rate ratio (IRR) for those in the newest cohort (1999/2000) at age 23 compared to the reference group was 0.53. In contrast, much higher IRRs were observed in the cohorts born from 1989-1992 and 1993-1998 (1.26 each).

The conclusion of the research team is that HPV immunization protects both vaccinated and unvaccinated women from high-grade cervical neoplasia. The best herd effect is expected at high HPV coverage rates, which could be facilitated through school-based programs.

Source:

Meglic E et al. Lancet Public Health 2026; 11: e35-e43; doi: 10.1016/S2468-2667(25)00297-X