HIV researchers suffered a blow at the weekend when drug company Merck pulled a major vaccine trial (BBC, AFP, AP, NY Times, press release). Testing of the V520 vaccine was stopped after it was found to be ineffective. “It is a huge disappointment because this vaccine has shown promise all the way through, but it’s only when you get in on these big trials that you start to see how the vaccine behaves. Although in earlier studies we saw beautiful immune responses, it doesn’t look like this immune response translates into something that could protect people against HIV infection,” said Glenda Gray, one of the principal investigators (AFP).

The vaccine used a weakened version of a common cold virus carrying three synthetic HIV genes. The trial enrolled 3,000 HIV-negative volunteers at high risk of HIV infection at sites around the world. An interim analysis conducted on half of these people found no benefit from the vaccine. There were 24 cases of infection in the 741 participants who received the vaccine and 21 cases in the 762 who didn’t.

Image: HIV virus / Getty