An influential government task force has drafted a recommendation that would for the first time urge doctors to offer a daily prophylactic pill to patients who are at risk for contracting H.I.V. The recommendation would include all men and women whose sexual behavior, sex partners or drug use place them at high risk of contracting the virus that causes AIDS.

The United States Preventive Services Task Force’s draft recommendation gave an “A” grade, the highest possible, to the regimen, known as PrEP, for pre-exposure prophylaxis. If approved, it would greatly expand access to the $20,000-a-year drug regimen, since most private health plans are required under the Affordable Care Act to cover the full cost of the preventive services recommended by the panel.

“This is definitely fantastic news and validates everything science has been saying all along,” said Dr. Aaron Lord, a physician at New York University School of Medicine who co-founded the PrEP4All Collaboration, which aims to expand access to PrEP for all Americans. “We’ve known this is a very effective medication for quite a while, and feel we could be a lot further along in using it to reduce infections. The potential is absolutely tremendous.”

“When taken daily, there’s very good evidence that the chance of acquiring H.I.V. is essentially zero,” Dr. Lord said.