The demand for monkeypox vaccines is outstripping the supply in New York City and Washington, D.C., two of the first cities in the US to offer inoculation against the virus.
The D.C. Department of Health announced that 300 appointments for the monkeypox vaccine would be available on Tuesday and Thursday, but those spots were already booked up by noon on Monday.
New York City also started offering the Jynneos vaccine at the Chelsea Sexual Health Clinic but all the appointments through Monday were filled.
Eligibility in both New York City and D.C. was limited to gay and bisexual men, as they are disproportionately affected by monkeypox. D.C. was also offering the vaccine to sex workers and staff at establishment where sexual activity occurs.
New York City has recorded at least 48 cases of monkeypox, while D.C. has recorded 16 cases.
Health officials said earlier this month that the U.S. government has 72,000 doses of the Jynneos vaccine in its stockpile.
The Jynneos vaccine is a two-dose regiment administered four weeks apart. An individual is considered fully vaccinated after the second dose.
The U.S. has about 100 million doses of an older smallpox vaccine, ACAM2000, but it has potentially serious side effects and CDC officials say there would be "serious discussion" before it is used.
The Associated Press contributed to this report.