A research trial for the PAVE-100 AIDS vaccine planned in the U.S. has been cancelled over concerns that additional research is needed to prove the vaccine is safe before it is tested on a large number of human subjects.

A similar vaccine from Merck was pulled from research trials last year after it failed to prevent infections and was found to have possibly increased recipients’ chances of contracting HIV.

The National Institute of Allergy and Infectious Diseases (NIAID) planned to test the PAVE-100 vaccine in 2,400 male volunteers at a cost of around $63 million, according to HealthNews.com.

Originally, the PAVE (Partnership for AIDS Vaccine Evaluation) vaccine was intended to be tested in 8,500 volunteers last October.

However, the trial was suspended after the failure of a similar HIV vaccine from Merck.

The Merck HIV vaccine was pulled from research trials last year after failing to prevent infections in research participants and failing to lower the amount of HIV in the blood of infected volunteers.

In addition, further evaluation determined the vaccine may have actually increased the risk of becoming infected by the virus.

The Merck vaccine was composed of a weakened version of a common cold virus, which delivered three synthetically produced genes from the AIDS virus.

The theory behind the vaccine was that the synthetic genes would stimulate T-cells in the body to provide a higher immune protection against the HIV virus.

Those infected with HIV who have strong T-cell response tend to do better than those who do not.

The PAVE-100 vaccine also used components from the cold virus as part of its delivery system.

Dr. Anthony S. Fauci, director of NIAID, stated the decision to suspend a large scale trial on the PAVE-100 vaccine stemmed from meetings with scientists in an attempt to understand why the Merck vaccine failed.

Dr. Fauci said more research was needed to determine the safety and efficacy of the new vaccine before testing it in a large number of human subjects.

“Show me that the vaccine works by lowering the amount of HIV in the blood,” Dr. Fauci told The New York Times.

“Then we will move to a larger trial that will document the link with a particular immune response.” Until the vaccine can be proven to lower HIV in the blood, Dr. Fauci stated that “doing a large trial is not justified.”

While the large scale trial for PAVE-100 has been cancelled, NIAID said in a statement that it “believes the vaccine… is scientifically intriguing and sufficiently different from previously tested HIV vaccines to consider testing it in a smaller, more focused clinical study.”

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