Gilead Sciences, maker of Truvada, the only drug approved to prevent infection with H.I.V., will donate enough of the drug to supply 200,000 patients annually for up to 11 years, federal health officials announced on Thursday.

Officials at the Department of Health and Human Services said the donation came about “as a result of discussions between the Trump administration and Gilead.”

The drug is taken once daily to prevent infection with H.I.V., a strategy called pre-exposure prophylaxis, or PrEP. An estimated one million Americans are at risk for infection and should be taking the pills, but only about 270,000 are doing so.

H.I.V. activists and experts had mixed reactions to the news. While some felt the donation was a good start, they said it filled only one-fifth of the need in the United States.