Some of the Covid-19 vaccines currently in development could increase the risk of acquiring HIV, warned a group of researchers in the The Lancet medical journal Monday, potentially leading to an increase in infections as vaccines are rolled out to vulnerable populations around the world. 

KEY FACTS

The researchers warn of a “cautionary tale” from efforts to create an HIV vaccine over a decade ago, where a promising vaccine candidate actually increased the risk of some men catching the virus.

The vaccine made use of a modified virus — called adenovirus 5 (Ad5) — as a vector to transport some of HIV’s genetic material into the body. 

Exactly how the vaccine increased the risks of HIV transmission is unknown, but a conference convened by the National Institutes of Health recommended against further use of Ad5 as a vector in HIV vaccines (Dr. Anthony Fauci was lead author of the paper outlining this position.)