The UK's Health Security Agency (UKHSA) has procured more than 20,000 doses of a smallpox vaccine made by Bavarian Nordic, as cases of monkeypox rise in Europe and beyond, it said on Thursday.

The vaccine is being offered to identified close contacts of people diagnosed with monkeypox to reduce the risk of symptomatic infection and severe illness, UKHSA said in a Twitter post.

In Europe, the Danish company's vaccine is approved only against smallpox, but is being used off-label for monkeypox, while in the United States it has been cleared for use against both smallpox and monkeypox.

The smallpox and monkeypox viruses are closely related. According to the World Health Organization, the first generation of smallpox vaccines were up to 85% effective in preventing monkeypox.

(Reporting by Natalie Grover in London;  Editing by Jan Harvey)