The U.S. National Institutes of Health has cancelled a study testing an experimental HIV vaccine because scientists concluded it did not prevent infection or reduce the amount of HIV in the blood. HIV is the virus that causes AIDS.
The so-called HVTN 505 study began in 2009 and is one of several such studies underway to find an effective AIDS vaccine. The study involved over 2,500 volunteers, specifically men who have sex with men and transgender people who have sex with men.
"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," Mitchell Warren, executive director of the nonprofit group AVAC: Global Advocacy for HIV Prevention, said in a statement.
While the failure of the vaccine is a blow to HIV vaccine research, the National Institutes of Allergy and Infectious Disease said it would continue to monitor the volunteers.
The experimental vaccine in the cancelled trials was based on a common cold virus. It was used to introduce HIV genes into the body to prime the immune system to provide a vaccine boost.
Matthew Rose, a participant HVTN 505 study, remained hopeful that an HIV vaccine will eventually be developed.
"These results do not change the fundamental view that an AIDS vaccine remains critical to any long-term strategy to end the AIDS epidemic," Rose told Reuters.
There are two traditional methods for creating a vaccine. One uses a weakened or attenuated version of a live virus to generate an immune response. The other uses a dead virus.
Both methods are proven to be safe and effective, except when it comes to HIV. Vaccine candidates produced by these methods simply have not been successful in people when it comes to the AIDS virus.
A Thai study from 2009 still has many hopeful. But even that study involving a vaccine known as RV 144 was judged to provide only 31 percent protection against HIV.