On Demand Antiretroviral Pre-exposure Prophylaxis for HIV Infection in Men Who Have Sex With Men

2 tablets of truvada within 24 hours before first sexual relations, then 1 tablet of Truvada during the period of sexual activity including the last sexual intercourse, finally, a last dose of 1 tablet of Truvada approximately 24 hours later

2 tablets of placebo within 24 hours before first sexual relations, then 1 tablet of placebo every 24 hours during the period of sexual activity including the last sexual intercourse, finally, a last dose of 1 tablet of placebo approximatively 24 hours later