Daily Pill Is 90 Percent Effective at Preventing HIV Infection 5.94K Max Read 11/24/10 03:33AM Filed to: Good News Good News Hiv Aids Drugs Pills Studies Research Medicine A massive new study appears to show that a daily dosage of common antiretroviral pill called Truvada to HIV-negative patients is 90 percent effective at preventing HIV infection. Terrific news! Too bad no one knows who'll pay for it.