Systematic Review of Orogenital HIV-1 Transmission Probabilities, R. F. Baggaley, R. G. White, and M. Boily, 37 International Journal of Epidemiology 1255-1265 (2008)

Believing that it is important to have a better understanding of the actual risks of HIV transmission through oral sex, the authors reviewed and summarized all available research literature, up to July 2007, on the risk of HIV transmission associated with oral sex between men, between women, and between men and women. The authors concluded that the available research was inadequate to determine the actual risk associated with oral sex. Because the risk of transmission is clearly very low, much larger studies would be required to assign a more precise statistical risk factor to oral sex. As the authors note, in cases where oral sex is reported as the only sexual conduct in which an interview was active, there is certainly the possibility of social desirability bias or other reasons why a higher risk interaction, particularly anal intercourse, might not be recalled. The takeaway: the risk of HIV transmission via oral sex is extremely low but greater than zero.