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New Vaccine for Human Papillomavirus 16/18 Shows High Levels of Immunogenicity: Presented at IDSA

By Ed Susman

PHILADELPHIA -- November 1, 2009 -- The new vaccine against human papillomavirus (HPV)-16/18 with adjuvant AS04 produces higher levels of antigens associated with immunogenicity than the similar vaccine directed at HPV strains 6/11/16/18, according to a study presented at the 47th Annual Meeting of the Infectious Diseases Society of America (IDSA).

"Higher immune responses with HPV-16/18 vaccine than HPV-6/11/16/18 vaccine were maintained up to month 18," said Mark Einstein, MD, Montefiore Division of Gynecologic Oncology, Albert College of Medicine, New York, New York, speaking at his late-breaker poster presentation here on October 31. "Differences in the magnitude of immune response between the vaccines may represent determinants of duration of protection," he explained.

The vaccines are directed against certain types of cancer-causing HPV. Types 16 and 18 cause about 70% of cervical cancer cases. Type 16 is also associated with oropharyngeal squamous-cell carcinoma.

Dr. Einstein and colleagues enrolled 1,106 women, half of whom were assigned to receive HPV-16/18 vaccine in 3 inoculations at baseline, 1 month, and 6 months, with the other half receiving HPV-6/11/16/18 vaccine administered at baseline, month 2, and month 6.

At month 18, in subjects seronegative for HPV before vaccination for the HPV type analysed, serum neutralising antibody geometric mean titres were 2.4- to 5.1-fold higher for HPV-16 and 7.9- to 9.8-fold higher for HPV-18 with HPV-16/18 vaccine than HPV-6/11/16/18 vaccine (P < .0001 for both).

Cervicovaginal secretions neutralising antibody positivity rates with HPV-16/18 vaccine and HPV-6/11/16/18 vaccine were 20.9% versus 14.0% for HPV-16 and 7.0% versus 0.0% for HPV-18. "The cervical area [is] where we want to see higher levels of these antibodies," Dr. Einstein explained.

The team also found that the percentage of responders was higher with HPV-16/18 vaccine than with HPV-6/11/16/18 vaccine for memory B-cells and CD4-positive T-cells. The frequency of circulating antigen-specific cells in responders was also higher with HPV-16/18 vaccine than with HPV-6/11/16/18 vaccine for memory B-cells and CD4-positive T-cells.

While there appear to be more local-site adverse events with the HPV-16/18 vaccine, Dr. Einstein said there were no differences in overall compliance or serious adverse events with either of the 2 vaccines.

The investigators are continuing to follow the patients in both cohorts.

Funding for this study was provided by GlaxoSmithKline, manufacturer of the HPV-16/18 vaccine.

[Presentation title: Comparative Immunogenicity of Two Prophylactic Human Papillomavirus Cervical Cancer Vaccines: Month 18 Results. Abstract LB-38]

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