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.
Medical Research: What should clinicians and patients take away from your report?
Response: Our findings, representing more than 140 million person-years of follow-up from 9 countries, provide strong evidence that HPV vaccination is highly effective outside trial settings, and reinforce the need for early vaccination and high vaccination coverage to maximize population-level effectiveness and herd effects.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: Our results are promising for the long-term population level effects of HPV vaccination programmes. However, continued monitoring is essential to confirm our findings. Future research should examine potential vaccine efficacy waning over time, type-replacement or lower vaccination coverage in groups at higher risk of HPV-related diseases. Finally, it will be important to include the population-level impact of HPV vaccination in low-income countries as they become available to increase our understanding of the potential herd effects of HPV vaccination in countries with substantial differences in sexual behaviour, HPV epidemiology and potential cofactors of HPV infection and diseases such as HIV prevalence.
Population-level impact and herd effects following human papillomavirus vaccination programmes: a systematic review and meta-analysis
Drolet, Mélanie et al.
The Lancet Infectious Diseases
Published Online: 02 March 2015
MedicalResearch.com Interview with: Marc Brisson, & Canada Research Chair in Mathematical Modeling and Health (2015). Strong Evidence HPV Vaccination Highly Effective Outside Trial Settings