HIV-1 and HIV-2 are two different viruses. HIV-1 is the main family of HIV and accounts for 95% of all HIV infections globally. HIV-2 is mainly seen in West African countries. The prevalence of HIV-2 in the rest of the world is negligible.

The risk of exposure to HIV-2 outside of West Africa is very low. Since 1987, there have been only 79 documented cases of HIV-2 infection in the United States. Of the 79 infected persons, 52 were born in West Africa, 1 in Kenya, 7 in the United States, 2 in India, and 2 in Europe.

Multiple clinical trials and years of clinical experience have shown that Truvada provides nearly perfect protection from HIV-1. This is the kind of HIV you are most likely to be exposed to anywhere outside of West Africa. Both HIV-1 and HIV-2 are found in West Africa. (For more detailed information on prevalence, see the 2016 UNAIDS Prevention Gap Report.)

For practical and ethical reasons, no clinical studies have investigated whether Truvada provides similar protection from HIV-2. That is why scientific and commercial literature says specifically that PrEP works against HIV-1. However, this does not mean PrEP users are at any significant risk of HIV-2. Clinical data from in vitro studies show that HIV-2 responds to the drugs in Truvada, and Truvada is part of the recommended treatment regimen for HIV-2 infection. Many doctors and researchers suspect that Truvada probably does provide protection from HIV-2.

Because Truvada is used in the treatment of both HIV-1 and HIV-2 and we have not seen breakthrough infections of HIV-2 among PrEP users anywhere (including West Africa), it seems likely that Truvada protects from HIV-2, as well. However, this has not been proven.