By Ludwig Burger and Rene Wagner

FRANKFURT/BERLIN (Reuters) – Germany will take a stake in unlisted biotech firm CureVac, which is working on a COVID-19 vaccine, four people familiar with the plan told Reuters on Monday.

Two of the sources described the size of the stake as substantial, without providing details.

Curevac, the German economy ministry and dievini Hopp BioTech holding, which is the investment vehicle of CureVac’s controlling shareholder Dietmar Hopp, declined to comment.

Dievini Hopp said in a statement earlier on Monday that it will join Economy Minister Peter Altmaier and CureVac’s acting Chief Executive Franz-Werner Haas for a press briefing at 1030 GMT, without providing details.

Reported attempts by the United States government to acquire Curevac or its assets in March stirred a political backlash in Germany, with Altmaier and Interior Minister Horst Seehofer at the time voicing support for keeping CureVac German.

Reflecting the sensitivity about ownership of the country’s two coronavirus vaccine developers – CureVac and BioNTech – Berlin in May gave itself new powers to veto hostile foreign takeover bids for healthcare companies.

(Additional reporting by Holger Hansen in Berlin and Patricia Uhlig in Frankfurt; Editing by Sabine Wollrab and Michelle Martin)