HPV Vaccine Very Effective against Cervical Cancer
The United States is behind in achieving high coverage with immunizations for adolescent girls against human papillomavirus (HPV) infections, a leading cause of cervical cancer, says Dr. Cosette Wheeler of the University of New Mexico Department of Pathology, one of the lead authors of two studies released Online First in The Lancet Oncology.
“These studies show the bivalent human papillomavirus (HPV) vaccine (Cervarix, GlaxoSmithKline) is even more effective than we had hoped. However, while some countries (Australia and UK) have achieved more than 80-90 percent coverage of adolescent girls with three doses of HPV vaccine, in the U.S. we are only at about 30 percent coverage. Other countries have been able to achieve high HPV vaccine coverage rates by governments providing resources to cover vaccine costs and implementation of infrastructures and voluntary school-based delivery programs.
"Clearly, our next step is to put in place the needed programs for successful delivery of HPV vaccines and other important adolescent vaccines which also need similar efforts. We should move our attention to achieving effective and equitable global implementation of these highly efficacious public health interventions. In low-resource countries where most cervical cancer occurs, HPV vaccination may be the only feasible approach to cervical cancer prevention. In the US, HPV vaccination of young adolescents prior to sexual exposure complements current secondary prevention efforts through cervical screening in women over their lifetime,” said Wheeler.
The bivalent vaccine targets HPV types 16 and 18 that are responsible for about 70% of cervical cancers. In 2009, the PApilloma TRIal against Cancer In young Adults (PATRICIA), the largest study of HPV16/18 vaccine efficacy to date, reported that the bivalent vaccine had high efficacy against the precancerous cervical lesions CIN2+.
Here, the researchers report the final PATRICIA analysis (after 4 years of follow-up). In young women not already infected with HPV, the vaccine proved over 93% effective against CIN3+ (a higher grade of abnormality more associated with invasive cervical cancer) and prevented 100% of adenocarcinoma (AIS) regardless of HPV type compared with nearly 46% efficacy against CIN3+ and 77% against AIS in the general population of women enrolled in the trial.
The authors conclude: “Appropriate effectiveness and implementation studies assessing the combination of vaccination and new screening strategies are warranted.”
In a second study, the vaccine showed increased cross-protection against other cancer-causing HPV types 31, 33, 45, and 51 in different cohorts representing diverse groups of women.
“There is a particularly high risk of HPV-33 infections progressing to cervical lesions, and HPV-45 is over-represented in adenocarcinoma…Our results show that cross-protective efficacy might provide substantial additional protection against cervical cancer beyond protection conferred against HPV-16/18 although the clinical benefit will need to be evaluated when delivered in real-world settings over the coming years,” concluded Wheeler.
The two studies show that the bivalent HPV vaccine will offer excellent protection against the more serious immediate precursor (CIN3) to invasive cervical cancer (ICC), particularly if given to young adolescent girls before they become sexually active. The findings also show the vaccine partially protects against four other cancer-causing HPV types not targeted by the formulation, that together with HPV16/18, cause about 85% of cervical cancer worldwide.
In a Comment published in the same issue of The Lancet Oncology, Drs. Mark Schiffman and Sholom Wacholder from the National Cancer Institute, Rockville, MD, USA remark: “We believe that increasing coverage, particularly of sexually-naïve adolescent females, is now the most important public-health issue in HPV vaccination efforts.”
They add: “We are particularly concerned about low vaccination rates in areas where cervical cancer incidence and mortality are high because of inadequate alternative prevention through effective cervical screening, and where nine of 10 cervical cancers deaths occur…The current vaccines are too expensive and difficult to deliver for many low-resource regions.”
For full Articles and Comment see:http://press.thelancet.com/tlopatricia.pdf
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