The U.S. emergency stockpile holds two vaccines approved by the Food and Drug Administration that could be used to contain monkeypox, officials at the Centers for Disease Control and Prevention told reporters on Monday.

The stockpile contains more than 100 million doses of the original smallpox vaccine. But that vaccine is associated with side effects and shouldn’t be given to certain patients, including those who are immuno-compromised.

A newer vaccine, called Jynneos, was approved in 2019 for prevention of both smallpox and monkeypox. More than 1,000 doses are held in the stockpile, Dr. Jennifer McQuiston, a deputy director at the C.D.C., said.

“We expect that level to ramp up very quickly in the coming weeks, as the company provides more doses to us,” she said. Doses have already been requested from the stockpile for inoculation of some high-risk contacts, she added.