This is the third PrEP trial, after FEM-PrEP and TDF2, for which an interim review of the trial’s data led to a change of course of the study. Because the four other arms of the VOICE trial continue, there are no data available publicly yet to explain why tenofovir would not show effectiveness in this study when three other studies showed a dramatic reduction in the risk of HIV infection with tenofovir alone or in combination with another antiretroviral (see table below). However, Sharon Hillier and Ian McGowan of the Microbicide Trials Network noted that the study’s population – predominately women in their 20’s, could be an important factor.
“If there’s one thing we’ve learned over the years it’s that unmarried women in their 20s are in a very different place in their lives than married women in their 30s. People in different circumstances will make different choices about their use of condoms, their choice of partners and whether or not to use a biomedical prevention product. As we continue the VOICE trial we recognize that there could be many factors that influenced the outcome with oral tenofovir, and even when we have more information available to us, understanding what exactly happened (or not) will not be simple.”
If confirmed (a full analysis of the data will not be available before several months) this would add to the challenge of defining a strategic use for PrEP in the general population or in populations at risk.