Wednesday, August 20, 2008

Is Gardasil cost effective?

Several strains of human papillomavirus (HPV) can cause cervical cancer, and two vaccines directed against the currently most important oncogenic strains (i.e., the HPV-16 and HPV-18 serotypes) have been developed.

Despite promising results from clinical trials, sufficient evidence of an effective long term vaccine against cervical cancer is lacking and the overall effect of the vaccines on cervical cancer remains unknown; the real impact of HPV vaccination on cervical cancer will not be known for decades.

The first vaccine against the HPV virus (Gardasil, Merck & Co) was licensed in 2006 for use in girls and women ages 9 to 26. Health officials recommend it for girls at age 11 or 12, and some doctors offer it to women in their 20s in "catch-up" vaccination campaigns. Merck also wants to market it to women ages 27 to 45, but so far the U.S. Food and Drug Administration has denied that request.

Gardasil is given in three doses over six months and costs about $375. It targets the two types of HPV, believed to be responsible for about 70 percent of cervical cancer cases, and two other types that cause most genital warts. The virus is spread by sexual activity.

Health officials say it's best to give the shots to girls at age 11 or 12, before they begin having sex. Some parents think that age is too young for a vaccination campaign against a sexually transmitted disease. But that is when the shots make the most economic sense, researchers found.

In the current edition of the New England Journal of Medicine, researchers used computer models to predict the health outcomes of girls and women who get the vaccination as well as Pap tests or other screenings, which are still recommended for vaccine recipients. Their calculation included the cost of the vaccine, screenings and treating cervical cancer and other illnesses targeted by the vaccine.

To determine cost-effectiveness, they used widely accepted economic measures of how much society is willing to pay to extend the life of a person by a year. They set a figure of $43,600 per year for the Gardasil vaccination of each 12-year-old girl, well below the $100,000 mark seen as an upper range for cost-effectiveness. However, the assumption is that the vaccine gives lifetime protection, which we don't know is true because the drug is too new and the data too preliminary.

The trends in the analysis suggested that as you get older, the vaccine becomes less cost-effective. This would imply that the earlier a female is vaccinated, the better the odds she will avoid HPV-caused cervical disease, thus lowering health-care costs in the long run.


New England Journal of Medicine (free full text)