Spain will start a "mix-and-match" COVID-19 vaccine trial to look into whether vaccines can be mixed for the first and second doses.
Officials say this comes as Spain has suspended the use of the AstraZeneca vaccine for people under 60.
They say the trial will be conducted on some 6-hundred people who have had a first dose of the AstraZeneca vaccine.
Their second dose could be either Pfizer's or Moderna's.
Similar tests are also happening in Britain, France and Germany.