Medical Research: What is the background for this study? What are the main findings?
Response: Since 2007, 52 countries have implemented human papillomavirus vaccination (HPV) programmes. Two HPV vaccines are currently available worldwide: the bivalent vaccine, which targets HPV types 16 and 18, causing 70-80% of cervical cancer, and the quadrivalent vaccine, which also targets HPV types 6 and 11, associated with 85-95% of anogenital wart cases. Large international randomised controlled clinical trials have shown both vaccines to be safe, well tolerated and highly efficacious against vaccine-type persistent infections and precancerous cervical lesions. Furthermore, both vaccines have shown some level of cross-protection against 3 HPV types (HPV 31, 33 and 45) not included in the vaccine and associated with a supplementary 10-15% of cervical cancers worldwide. Now that 7 years have elapsed since the implementation of the first HPV vaccination program, we verified whether the promising results from clinical trials are materialising at the population level. We conducted a meta-analysis to examine the population-level impact in countries that have introduced HPV vaccination programs.
In countries with high female vaccination coverage (<50%), our main findings indicate:
- sharp declines in HPV-related outcomes among females targeted for vaccination (e.g., HPV-16/18 infection and anogenital warts declined by more than 60% in females younger than 20 years), and
- evidence of cross-protection with significant reductions in HPV-31/33/45 infection among females younger than 20 years
- evidence of herd effects (indirect benefit of vaccination among unvaccinated individuals) with significant reductions in anogenital warts among males and older females.
In countries with low coverage (<50%), we report:
- significant reductions in HPV-16/18 infection and anogenital warts among young females, with no indication of herd effects or cross-protection. Continue reading