Two new Cochrane reviews by UK researchers provide strong, consistent evidence that human papillomavirus (HPV) vaccination helps prevent cervical cancer, sharply reduces high-grade precancerous lesions, and is not linked to serious adverse events, especially when administered to young people who haven’t been exposed to the virus. The findings underscore the importance of early adolescent vaccination.
The reviews span both randomized controlled trials (RCTs) and large population-level studies, drawing on data from more than 132 million people.
80% reduction in cervical cancer
A population-level analysis included 225 studies from 46 countries and found an 80% reduction in cervical cancer among girls vaccinated by age 16 (risk ratio [RR], 0.20). Risk reductions were smaller among those vaccinated later in adolescence or in adulthood.
The review also reported moderate-certainty evidence that vaccination lowers rates of precancerous cervical lesions and the incidence of anogenital warts.
The review also found no evidence linking HPV vaccination to widely discussed harms, including infertility, chronic fatigue syndrome (also known as myalgic encephalomyelitis), Guillain-Barre syndrome, and complex regional pain syndrome.
A separate analysis of RCTs evaluated four HPV vaccines approved by the World Health Organization (WHO)—Cervarix, Gardasil, Gardasil-9, and Cecolin—across 60 trials including 157,414 participants.
While the trials did not last long enough for cancers to develop, the vaccines reduced high-grade vaccine-matched precancerous cervical lesions 60% (RR, 0.40) in females ages 15 to 25 after six years. A pairwise analysis of 39 studies showed that rates of serious adverse events did not differ between the vaccine and control groups (RR, 0.99) at up to 72 months follow-up.
Geographic gaps, need for longer-term research
The two reviews “provide the most comprehensive and up-to-date evidence on HPV vaccination to date,” notes a Cochrane press release. Still, the authors highlight some evidence gaps and limitations. Most of the research was conducted in high-income countries, so more research is needed in lower- and middle-income countries where cervical cancer screening programs are lacking. The researchers also call for more long-term studies.
“Longer-term data will continue to strengthen our understanding of how HPV vaccination protects against cancer over a lifetime,” senior author Jo Morrison, DPhil, gynecologic oncology consultant at Somerset NHS Foundation Trust and honorary associate professor at the University of Exeter, says in the release. “Whilst we now have sufficient data to see a beneficial effect of HPV vaccination on cervical cancers, which tend to develop in younger women, it will take decades to fully understand the impact of vaccination on vulval, peri-anal, penile and head and neck cancers, which often develop later in life.”
