Two vaccines against cervical cancer are being widely used without sufficient evidence about whether they are worth their high cost or even whether they will effectively stop women from getting the disease, two articles in this week's New England Journal of Medicine conclude. Both vaccines target the human papillomavirus, a common sexually transmitted virus that usually causes no symptoms and is cleared by the immune system, but which can in very rare cases become chronic and cause cervical cancer. The two vaccines, Gardasil by Merck Sharp & Dohme and Cervarix by GlaxoSmithKline, target two strains of the virus that together cause an estimated 70 percent of cervical cancers. Despite great expectations and promising results of clinical trials, we still lack sufficient evidence of an effective vaccine against cervical cancer," Dr. Charlotte J. Haug ... wrote in an editorial in Thursday's issue of The New England Journal. "With so many essential questions still unanswered, there is good reason to be cautious." The vaccines have been studied for a relatively short period - both were licensed in 2006 and have been studied in clinical trials for at most six and a half years. Researchers have not yet demonstrated how long the immunity will last, or whether eliminating some strains of cancer-causing virus will decrease the body's natural immunity to other strains. Because cervical cancer develops only after years of chronic infection with HPV, Dr. Haug said there was not yet absolute proof that protection against these two strains of the virus would ultimately reduce rates of cervical cancer.

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