Picking the endpoints

It is not possible to directly demonstrate an HPV vaccine's ability to prevent cervical cancer because it takes decades for infection to cause cancer, and the standard of care is to screen for and excise precancerous lesions. Merck & Co. Inc. and GlaxoSmithKline plc took different approaches to get around this issue.

Given the problem in showing direct clinical efficacy, FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) issued recommendations to FDA on efficacy endpoints for HPV vaccines in November 2001. ...