Doctors used the smallpox vaccine to prevent the transmission of monkeypox. Smallpox is more severe than monkeypox, but both have similar symptoms.
By June 2003, at least 30 people received the smallpox vaccine, including 28 adults and two children, according to the archived CDC site.
The vaccine was given pre-exposure to some and post-exposure to others.
“No serious adverse events were reported following smallpox vaccination,” according to the CDC site.
Source : https://www.businessinsider.co.za/heres-how-the-us-handled-its-first-ever-monkeypox-outbreak-2022-5