The company has deals with EU countries for the supply of up to 460 million doses.
The trial will draw on a sample of 600 people of all ages from across Spain
Under the proposal, patients would receive a second shot of vaccines produced by Pfizer and Moderna after eight weeks
The logo of Spanish pharmaceutical firm Rovi.
This would be the first European drug ingredients production site for Moderna outside of Switzerland.
The government intends to have 70% of the 47 million population vaccinated by the summer.
Packets of Moderna COVID-19 vaccine.