The US Centers for Disease Control and Prevention says people who received at least one shot of the two-dose monkeypox vaccine are 14 times less likely to be infected.

The CDC analyzed cases of more than 5,400 males aged between 18 and 49 reported from late July through early September.

It says the onset of illness at least 14 days after at least one dose of the vaccine was about one-fourteenth of that among the unvaccinated.

The vaccine was originally developed for smallpox, and is believed to be effective for monkeypox. Actual efficacy is unknown.

Professor Morikawa Shigeru at the Okayama University of Science says the study confirms a certain level of efficacy.

But he also points out that the study only relates to one dose of what is a two-dose vaccine. He says further analysis will be necessary to see properly determine immunity.

The CDC says as of Thursday, 76,713 cases of monkeypox had been reported globally in 109 countries and territories. It says 36 died.

Vaccinations are moving ahead mainly in the United States and Europe.