New York City -- Authorities began offering monkeypox vaccinations this week, but the demand was so high that walk-in appointments had to be cut off.

Thirty people have tested positive for orthopoxvirus in New York City as of Thursday, according to NYC Health, adding that "all cases are likely monkeypox."

To curb the outbreak, authorities started offering a monkeypox vaccine Thursday, with eligible New Yorkers able to make an appointment or walk into the Chelsea Sexual Health Clinic to get the vaccine.

"As I have said since day one, we are prepared, not panicked and this monkeypox vaccination site is one more critical tool to keep New Yorkers healthy," New York City Mayor Eric Adams said in the NYC Health news release Thursday. "Starting today, eligible New Yorkers who may have been exposed to monkeypox can now get vaccinated to stay safe and slow the spread."

However, walk-in appointments had to be cut off within three hours of the launch because the demand was so high, reported NBC New York. At the time, the outlet counted about 100 people in line outside the clinic.

The agency urged those interested in getting the vaccine to check back Sunday for new appointments next week, as the slots are already filled until Monday, June 27. Those eligible for the vaccine may register for the monkeypox vaccination through this page.

"Unfortunately, walk-in vaccinations will also not be available at this time," noted NYC Health. "We are requesting additional supply from the CDC to meet the high demand."

Cases in New York City rose by a whopping 60% in the past week alone, according to NBC New York, noting that the city accounts for 20% of all the cases nationwide. In the U.S. case count of total monkeypox/orthopoxvirus cases by state, New York is second to California, which had logged 48 cases as of 2 p.m. ET Thursday.

Worldwide, the U.K. still has the highest number of confirmed cases, with 793 as of 5 p.m. EDT Thursday. Germany follows this with 592, and Spain with 520.

So far, most of the cases in New York City had mild symptoms and the individuals did not require hospitalization, noted NYC Health. Those who develop monkeypox symptoms or a "new or unexpected" rash should contact their health care provider.