The medicines regulator Swissmedic says it has not yet received enough robust data from clinical trials to give the green light to the Covid-19 vaccine developed by the Swedish-British company.

While the supervisory authority saw conclusive results from studies involving many participants to approve two other coronavirus vaccines, the same could not be said for the Oxford-AstraZeneca shot, Swissmedic director Raimund Bruhin told the CH Media group of newspapers on Thursday.

But this did not mean that he believes the vaccine is a poor one.

“We are only saying that the company has not yet been able to prove to us that it is a good vaccine,” said Bruhin.

The approvals process, he added, was about hard data and facts. Last week Swissmedic received a large package of data from the pharmaceutical company, which it is now reviewing, and remains in regular contact with the makers of the vaccine.

Other countries, such as the United Kingdom, have been administering the AstraZeneca vaccine for over three months – although several nations have halted vaccinations in recent days over isolated cases of blood-clotting. The European Medicines Agency has said the benefits of the Oxford-AstraZeneca jab greatly outweigh the risks and on Thursday will issue a report on its investigation into cases of blood clots.

Switzerland has ordered more than 35 million doses of Covid-19 vaccines from five manufacturers. To date Swissmedic has approved shots developed by Pfizer/BioNTech and Moderna. Roughly 4% of the population has been vaccinated so far, but delays in approval and delivery have slowed the roll-out process.