News release

From: The Lancet

The Lancet Public Health: School-based HPV vaccination programmes provide protection to unvaccinated women via herd immunity, study suggests

School-based HPV (Human papillomavirus) vaccination programmes are associated with a significantly reduced risk of serious pre-cancerous changes in the cervix in both vaccinated women, through direct protection, and unvaccinated women through herd immunity, according to a paper published in The Lancet Public Health journal.

HPV is a common sexually transmitted infection and the main cause of cervical cancer. HPV vaccination is known to greatly reduce the risk of serious cervical changes in people who are vaccinated, but it has been less clear whether it also protects those who are not vaccinated.

The study analysed Swedish national health registry data from over 800,000 unvaccinated women born between 1985 and 2000. The study compared rates of pre-cancerous changes in the cervix across birth cohorts exposed to different HPV vaccination strategies in Sweden: opportunistic vaccination (1985-1988), subsidised programmes (1989-1992), catch-up programmes (1993-1998), and school-based vaccination (1999-2000).

The study found that unvaccinated women born in 1999 and 2000 in Sweden, who grew up alongside peers vaccinated through a school-based programme, had about half the risk of developing serious precancerous changes in the cervix compared with unvaccinated women born between 1985 and 1988, when vaccination uptake was lower and only given to women who sought it out.

The authors say the results suggest school-based HPV vaccination programmes play an important role as a cost-effective strategy to reduce cervical disease and cancer risk not only in vaccinated individuals, but across entire populations. However, they also note that as an observational study, the findings may be affected by other factors, such as differences between birth cohorts in sexual behaviour, cervical screening participation, testing practices, and access to healthcare.