MedicalResearch.com Interview with:
Dr Julia Brotherton
Victorian Cytology Service, Melbourne, Victoria, Australia
Dr Elizabeth Crowe
The University of Queensland, School of Population Health, Brisbane, Australia
NHS Borders, Department of Public Health, Melrose, Scotland, UK
Prof. David Whiteman
Group Leader / Department Coordinator
QIMR Berghofer Medical Research Institute
Royal Brisbane Hospital, QLD 4029
MedicalResearch.com: What are the main findings of the study?
1. We conducted a case-control study in which we retrieved the HPV vaccination histories of young Australian women who were notified to the Pap smear registry with high-grade cervical lesions or with other types of cervical lesions, and compared them with the vaccination histories of women whose Pap smears showed only normal cytology.
2. We found that women with high grade cervical lesions were significantly less likely than women with normal cytology to have received 3 doses of the quadrivalent HPV vaccine, equivalent to a vaccine effectiveness of 46%.
3. The vaccine effectiveness among 15-19 year old women was even higher at 57%. We believe this reflects the fact that HPV16 causes an even higher proportion of high grade disease in young women due to its higher oncogenicity and shorter latent period.
4. The HPV vaccine had 34% effectiveness against other cervical lesions (i.e. those not proven to be high grade lesions on histology).
5. We also observed that 2 doses of the vaccine were 21% effective in preventing both high grade lesions and other grade lesions.
MedicalResearch.com: Were any of the findings unexpected?
1. Before this study was performed, we did not know whether less than three doses of vaccine would provide any protection. Our findings that 2 doses conferred 21% protection against both high grade lesions and other lesions are encouraging, but suggest that three doses are required for best protection using the current dose schedule.
MedicalResearch.com: What should clinicians and patients take away from your report?
1. This report demonstrates the effectiveness of the HPV vaccine in the ‘real world’ population setting (i.e. outside of clinical trials).
2. The vaccine is targeted against two HPV types (16 and 18) that are known to cause about 50% of high grade cervical lesions. Among women receiving the vaccine, we observed a 46% reduction in the risk of high grade lesions, consistent with the vaccine preventing almost all high grade lesions that are caused by HPV 16 and 18.
3. Importantly, because the vaccine does not target other HPV types known to cause the remainder of high grade lesions, it is essential that women continue to be screened, even if they have received the vaccine.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
1. We need to continue to monitor trends in HPV vaccination rates, and also closely monitor trends in cervical lesions and cancers into the future as it is predicted that vaccine effectiveness will be seen to improve with longer follow-up times.
2. The performance of the Pap smear programs must be monitored to rapidly flag any changes in screening practices among women.
3. While we estimated the effectiveness of 2 doses of the vaccine as 21%, this needs to be confirmed in other studies.