The European Union's drug watchdog is in talks with the maker of a vaccine against deadly smallpox to extend its use to monkeypox, a senior official said Thursday.

The European Medicines Agency (EMA) said it was working with the manufacturer of the Imvanex jab "out of precaution" to ensure it had supplies if needed.

"Despite the outbreak being rather unprecedented in Europe, at present this is not a public health emergency," EMA vaccines chief Marco Cavaleri said.

Monkeypox is related to smallpox, which killed millions around the world every year before it was eradicated in 1980, but has far less severe symptoms.

The WHO says more than 550 monkeypox cases have been confirmed in 30 countries outside the West African nations where it is endemic since the start of May.

Imvanex, made by Danish firm Bavarian Nordic, was authorised by the EMA in 2013 for smallpox, but the maker did not apply at the time for its use against monkeypox.

"The EMA emergency task force is in talks with (maker) to prepare for the submission of data that could support an extension of indication" to monkeypox, Cavaleri said.

Animal data showed that Imvanex was "effective" against monkeypox, he added.

The vaccine would most likely be given to close contacts of people infected with monkeypox to prevent its spread.

The EMA hoped the firm could apply "as soon as possible", Cavaleri said, without giving a timeframe.

The watchdog was also ready to discuss how to increase manufacturing capacity, given that smallpox jabs are in short supply due to its eradication more than four decades ago, he said.

The European Commission told AFP last week it was already working on centralising purchases of vaccines and treatments for monkeypox.

The US has said it has around 1,000 doses of Imvanex, where it is known as JYNNEOS and is already authorised for smallpox.