Switzerland has withheld approval for AstraZeneca's Covid-19 vaccine, drugs regulator Swissmedic said on Wednesday, demanding more efficacy and quality data before greenlighting a shot that won European Union approval last week.
The country separately announced it had ordered millions more Covid-19 vaccine doses from other manufacturers.
Switzerland, which has already ordered 5.3 million doses from AstraZeneca, said it was awaiting results from trials of the shot in North and South America involving tens of thousands of people, after earlier trials did not produce clear data including on efficacy in older people.
"As soon as the results have been received, a temporary authorisation according to the rolling procedure could be issued at very short notice," Swissmedic said in a statement, adding it was necessary to get additional data about safety, efficacy and quality.
"The data currently available do not point to a positive decision regarding benefits and risks," it said.
AstraZeneca reiterated that its vaccine was being reviewed on a rolling basis by Swissmedic, to speed up the approval process, and that it would share information with the regulator as quickly as it became available.
"We are confident that our vaccine is effective, well-tolerated, and can have a real impact on the pandemic," the company said.
AstraZeneca and its partner, Oxford University, have defended their vaccine that is approved in about 50 countries, saying it had 76% efficacy against symptomatic infection for three months after a single dose, which increased if the second shot is delayed.
However, some European countries are restricting it to certain age groups, citing a lack of data in particular in older people.
The Swiss government said it had signed a deal with Germany's Curevac and the Swedish government for the delivery of 5 million vaccine doses, a preliminary pact with U.S. vaccine maker Novavax for 6 million doses, and secured a further 6 million doses from Moderna.
These new orders bring total Swiss vaccine orders to more than 30 million doses, enough to vaccinate its 8.6 million population about twice over under a two-dose regimen.
Further talks with additional developers are taking place for even more shots, the government said.
"The idea behind procuring vaccines from different manufacturers is to make sure that sufficient doses of an approved vaccine are available to the public even if there are delivery problems," the Federal Health Ministry said.