BRUSSELS, Sept 7 (Reuters) - The European Union said on Wednesday it had secured an additional 170,920 doses of the monkeypox vaccine developed by biotech firm Bavarian Nordic amid concerns about the outbreak of the disease.

The new order more than doubles the EU's supply of the vaccine, bringing the total number of doses directly purchased by the EU to nearly 335,000.

The additional doses will be available for delivery before the end of the year, while shots that were purchased earlier are currently being distributed, the EU Commission said.

"While we have seen the number of monkeypox cases decreasing in the EU over the past weeks, the threat has not passed, and we cannot let down our guard," EU health commissioner Stella Kyriakides said.

Since the start of the outbreak around 18,500 cases of monkeypox have been reported in EU countries and partners Norway and Iceland. (Reporting by Francesco Guarascio @fraguarascio; editing by Jason Neely)