SÃO PAULO, Brazil — Seeking to stem a sharp rise in H.I.V. cases among young people, Brazil began offering a drug this month that can prevent infection to those deemed at high risk.

Brazil is the first country in Latin America, and among the first in the developing world, to adopt the pill Truvada, under a program known as PrEP, short for pre-exposure prophylaxis, as an integral part of its preventive health care policy.

The blue pill — which drastically reduces the risk of contracting the virus when taken daily — will be made available at no cost to eligible Brazilians at 35 public health clinics in 22 cities during an inaugural phase of the program.

The Brazilian Health Ministry is paying Gilead Sciences, the American manufacturer of the drug, about 75 cents a dose, a fraction of the price users pay in the United States, where the pill sells for upward of $1,600 for a month’s supply.