Switzerland has refused to approve the Oxford AstraZeneca Covid vaccine for use in the country.
It is the latest country to have concerns over the effectiveness of the vaccine in over 65's - after similar worries in France, Germany and Austria.
Dr Claus Bolte, head of authorisation at medicines regulator Swiss Medic, said it had requested more information from AstraZeneca after deciding not to sign-off on the use of the Oxford vaccine in Switzerland.
He told BBC Radio 4’s Today programme his team were “not satisfied with the data we have received”.
Dr Bolte said the precise details of their concerns were confidential but added: “What I can say is that yes, it pertains to different age groups, over-65s and over-55s as well.
“It pertains to comorbidities, pre-existing conditions like asthma, hypertension, diabetes.
“It also pertains to the way some laboratories assessments were made.”
He added that the results of large-scale clinical trials in the US and South America using the Oxford vaccine would help to provide more sufficient data.
