"What people should do is look at what the MHRA say, our independent regulator - that's why we have them, that's why they are independent", Johnson said, when asked about the issue during a visit to AstraZeneca's manufacturing plant in Macclesfield, north-west England.
Cavaleri added that the regulator would not be in a position to offer advice on what age groups the jab should be given to.
A top official in the European Medicines Agency said in an interview published Tuesday that there is a link between the AstraZeneca coronavirus vaccine and blood clots. Several countries had stopped using the vaccine ahead of that decision to wait for the EMA's initial findings.
But it added that a causal link between clots and the vaccine is possible and the EMA is expected to provide an updated assessment on the investigation this week.
It said that the committee had "not yet reached a conclusion and the review is now ongoing", but it is expected to announce findings on Wednesday or Thursday. Should the United Kingdom government restrict access to AstraZeneca, the speed of their vaccine rollout could be greatly slowed down.
As the number of blood-clot reports rises, EMA vaccine chief Marco Cavaleri told the Italian newspaper il Messaggero it's "clear that there is an association with the vaccine", as translated by Reuters.
Fully vaccinated Americans can travel safely again, CDC says
We are not recommending travel at this time, especially for unvaccinated individuals", Walensky said. The CDC cited recent research on the real-world effects of the vaccines for its updated guidance.
The EMA is investigating 44 reports of an extremely rare brain clot known as cerebral venous sinus thrombosis (CVST) out of 9.2 million people who have received the vaccine in the European Economic Area, which comprises European Union member states and Iceland, Liechtenstein and Norway.
The UK has secured a total of 457 million Covid vaccine doses, of which 100 million are from AstraZeneca.
It recently said that it identified 30 cases of rare blood clot events out of 18.1 million doses of the jab administered up to and including March 24.
The EMA has consistently said that "The benefits of the AstraZeneca vaccine in preventing Covid-19, with its associated risk of hospitalisation and death, outweigh the risks of side effects".
Authorities had pledged to administer at least 4 million first doses of the vaccine by end-March, but could only vaccinate 670,000 after the European Union blocked AstraZeneca vaccine exports to Australia in the wake of the drugmaker's failure to meet its shipment pledge to the bloc.