The National Institutes of Health halted a study on an experimental HIV vaccine Thursday after an independent review board found the vaccine failed to prevent infection.
The government study, called HVTN 505, had 2,504 volunteers in 19 U.S. cities. All of those enrolled in the trial, which began in 2009, were either men who have sex with other men or transgender people who have sex with men.
The review board recommended the NIH vaccine stop being given to subjects, after a scheduled safety review April 22 showed slightly more subjects who had taken the vaccine later became infected with HIV, the virus which causes AIDS. The review found 41 cases of HIV infection occurred in volunteers who received the vaccine. It also showed the vaccine failed to reduce the amount of HIV found in the blood.
The National Institute of Allergy and Infectious Diseases (NIAID), a branch of the NIH intends to continue studying the subjects of the trial. Fewer people, only 30 cases, contracted HIV when given a dummy vaccine, but the NIAID believes the risk is not statically significant. They said the increased occurrence of HIV in those who received the real vaccine could simply be due to chance.
HVTN 505 included a two-part vaccine strategy aimed at first priming the immune system and then using a vaccine “boost.”
The vaccine was based on a common cold virus equipped with HIV genes designed to get the immune system’s attention.
"This trial has provided a clear, swift answer about a specific vaccine strategy. It's not the answer we hoped for, but the search doesn't end here," executive director of the nonprofit group AVAC: Global Advocacy for HIV Prevention Mitchell Warren said in a statement.
"Researchers need to unpack the data from this trial to understand more about why this strategy didn't prevent infection," he added.
There is currently no approved vaccine for the prevention of HIV.