HIV-negative people may falsely test postive after clinical vaccine trials

A recent study showed that nearly half the HIV-negative people who participate in clinical trials for potential vaccines end up testing positive although they are not infected with the virus.

Dr. Michael Horberg, director of HIV/AIDS at Kaiser Permanente in Santa Clara, California, told that the results are because participants underwent what is known as vaccine-induced seropositivity/reactivity, which means that they have immune system antibodies to the virus, but not the virus itself.

“You need to make sure to use other forms of testing for HIV, for example, viral load or p24 antigen, not just HIV antibodies,” Horberg told “And people who've been in trials need to know their antibody status by the end of the trial. If it is a false positive but they do not have HIV infection, that would be very important for them to know, especially if they do repeat testing as part of good preventive health.”

The findings were announced at the International AIDS Conference in Vienna and published in the July 21 issue of the Journal of the American Medical Association.

Of the 2,200 participants in HIV vaccine trials studied, 41.7 percent underwent VISP and tested positive for HIV antibodies, according to the study, reports.

A second study, which was also presented at the conference, showed that a screening program used in emergency departments did not turn up very many new cases of HIV, according to the report.