A US-based HIV vaccine trial is expanding the number of participants it will enroll as well as the scientific questions it will probe.
Conducted in 12 US cities, the HIV Vaccine Trials Network 505 (HVTN 505) study will assess a dual vaccine candidate for safety and whether it can prevent infection, not just curb the virus in a person already infected. Enrollment is increasing from about 1,300 men who have sex with men, and transgender women who have sex with men, to 2,200.
The trial’s scientific scope changed in response to the RV-144 trial in Thailand in 2009, which proved it was possible to for a vaccine to prevent HIV infection. Though the vaccine’s efficacy was too low, the research offered the first-ever evidence that an HIV/AIDS vaccine candidate conferred even modest protection against infection.
"Because of the Thai trial, what we saw in that vaccine actually preventing infection was, wow, we really need to then look differently at HVTN 505 and expand its ability to look at the question: could this vaccine actually also prevent infection, prevent acquisition of HIV?" said Mitchell Warren, head of the AIDS Vaccine Advocacy Coalition (AVAC). Previously, a main outcome was whether a candidate lowered viral load in vaccinated persons who later became infected.
The HVTN 505 trial will assess whether the vaccine candidate stimulates both an antibody response to prevent HIV infection and a cell-mediated immune response to mitigate infection, said Warren.
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