Studies Confirm Long-term Protection Against Precancerous Cervical Lesions With Vaccines Against Human Papilloma Viruses (HPV)

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Main Category: Cervical Cancer / HPV Vaccine
Also Included In: Immune System / Vaccines;  Women's Health / Gynecology
Article Date: 18 Apr 2007 - 9:00 PDT

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Follow-up studies of two vaccines against HPV causing cervical cancer have shown long-term protection against precancerous lesions, according to results reported at the 2007 Annual Meeting of the American Association for Cancer Research (14-18 April, 2007; Los Angeles, USA).

Results from long-term follow-up of women vaccinated with a candidate vaccine against HPV types 16 and 18 (Cervarix, being developed by GlaxoSmithKline) showed 100% efficacy in preventing precancerous lesions due to these virus types for up to 5.5 years. The initial study was a double-blind, controlled trial of 1113 women (aged 15-25 years) who were randomised to receive three doses of the vaccine or placebo at 0, 1 and 6 months.

The extended follow-up included 776 women who were followed for up to 67 months. The vaccine induced a strong immune response in virtually 100% of women, which was sustained out to 5.5 years for both HPV types 16 and 18. At the end of the follow-up period, the average level of antibodies against both virus types was at least 11 times higher than those associated with natural infection.

Results showed 68% efficacy against precancerous lesions (CIN2+) and 38% efficacy against abnormal Pap smears, regardless of the type of cancer-causing virus detected. Further results showed that the vaccine provided significant protection against genetically similar viruses, with 88% efficacy against HPV 45 and 54% against HPV 31.

Stanley Gall, professor of obstetrics, gynaecology and women's health at the University of Louisville, Kentucky, USA, reported: "These new data demonstrate the longest duration of protection seen in any cervical cancer vaccine trial reported to date. They are exciting for the prevention of cervical cancer in women around the world."

Results from long-term follow-up of women given a quadrivalent HPV vaccine (Gardasil) also demonstrated sustained protection against precancerous lesions. A total of 21,000 women (16-25 years) in four cohorts have now been randomised to vaccine or placebo at day 1, and months 2 and 6. Efficacy in women receiving all three doses was 99-100%.

The vaccine proved highly effective against cervical intraepithelial neoplasia grades 2 and 3, precancerous lesions that are frequently caused by HPV 16. Only a single woman in the vaccine group presented with an early HPV type 16 lesion, compared to 42 in the placebo group with HPV 16 or 18 related cervical intraepithelial neoplasias of grades 2 or 3, or adenocarcinoma.

Darron Brown, professor of medicine, microbiology and immunology at Indiana University School of Medicine, reported: "After three years, we see that the vaccine remains highly effective against HPV 16 and 18 related precancerous cervical and other genital lesions caused by these HPV types. The high degree of efficacy and safety of this vaccine is remarkable." He noted that results from a study of cross-protection were 'very encouraging' but would not be available for a few more weeks.

Written by: Susan Mayor PhD
Freelance medical journalist


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