COLUMBIA, S.C. (AP) — South Carolina health officials on Friday began using a recently approved plan to expand the number of monkeypox vaccines available as the state sees increased case numbers.

The method, authorized by U.S. health officials more than two weeks ago, involves giving the shot under the first layer of skin rather than into the fat layer found deeper in the tissue. The decision comes amid 100 reported cases of monkeypox in the state, according to the South Carolina Department of Health and Environmental Control.

Over one-third of cases in South Carolina were reported in the Midlands. As of Friday, the state reported receiving 4,287 doses of the vaccine and administering 860.

A 2015 study showed that 94% of people who received one-fifth of the vaccine had sufficient antibody levels.

“With vaccine supply being limited nationally, it is important that we find ways to meet the needs and demands of those at higher risk of exposure to monkeypox,” Dr. Linda Bell, a state epidemiologist, said in a news release.

To that end, state health officials also expanded eligibility for the vaccine. The list now includes men having sex with men who have had either a sexually transmitted infection in the past 90 days or multiple sex partners over that period; and anyone receiving HIV PrEP treatment.

Men who have sex with men make up about 95% of all cases nationwide, according to a Medical University of South Carolina news release.

“It’s very clear that if you’re a sexually active gay man, you should try to get a vaccine. You’re the absolute highest-risk group,” Dr. Scott Curry said in the release.