The National Institute of Allergy and Infectious Diseases (NIAID) announced last week that it will stop the experimental vaccine injections in its HVTN 505 Phase IIb clinical study. An independent monitoring board found during an early review of the data (April 22) that the HIV vaccine did not prevent infections nor lower HIV levels in those people who became infected.
HVTN 505 started in 2009 in 21 sites throughout the US. It enrolled 2,504 participants: 1,250 got the experimental vaccine while 1,244 got placebo injections.
Study participants received 4 injections over 24 weeks with two different products. The first was a DNA priming vaccine that contained non-infectious particles representing certain proteins from the surface and internal genetic structures of HIV. The second was a “booster” vaccine of matching particles. Particles from all three major HIV subtypes were included.
During the first 28 weeks of the study, 14 infections occurred in the vaccine group while 9 infections occurred in the placebo group. In the April 22 analysis (with data over two years), 27 infections occurred in the vaccine group while 21 infections occurred in the placebo group. There was no statistical difference between the groups despite a higher number of infections in the vaccine group.
Additionally, the board found that the vaccine did not lower viral load either. The analysis looked at those participants who had gotten HIV at least 28 weeks after starting the study and who were also followed for at least another 20 weeks after diagnosis.
People who got the vaccine product and who became infected with be followed by NIAID and the study team to further analyze the data, which will hopefully lead to some conclusions as to why the vaccine failed to prevent infections.
The NIH has created a Q&A about this early study closure.