The Prime Minister has urged people to get their Covid-19 vaccine when invited, after concerns were raised about potential side effects of the Oxford/AstraZeneca jab.
Boris Johnson said getting the population vaccinated was “the key thing”.
It comes as regulatory bodies from the UK and Europe are assessing data on the jab and a potential association with a rare form of blood clot.
And the World Health Organisation (WHO) has confirmed that it will also convene a panel of experts to assess the information.
The WHO and the European Medicines Agency (EMA) have confirmed they will publish findings later this week.
Mr Johnson defended the AstraZeneca Covid-19 vaccine as he visited the pharmaceutical giant’s manufacturing plant in Macclesfield.
“On the Oxford/AstraZeneca vaccine, the best thing people should do is look at what the MHRA (Medicines and Healthcare products Regulatory Agency) say, our independent regulator – that’s why we have them, that’s why they are independent,” he said.
“Their advice to people is to keep going out there, get your jab, get your second jab.”
He added: “The best thing of all is to vaccinate our population, get everybody out getting the jab, that’s the key thing and that’s what I would advocate, number one”.
It comes after reports that a senior EMA official told an Italian newspaper there appears to be an association with the vaccine and rare blood clots.
Marco Cavaleri, head of vaccines at the EMA, is said to have suggested a clear link, though admitted there was uncertainty how the vaccine would cause the complication.
When asked about the remarks, Dr Rogerio Pinto de Sa Gaspar, director of regulation and prequalification at the WHO, said: “As we were in this briefing, there was a denial from the European Medicine’s Agency concerning the existence of the link.”
The EMA’s said that its safety committee has “not yet reached a conclusion and the review is currently ongoing” but it is expected to announce findings on Wednesday or Thursday.
Dr Pinto de Sa Gaspar added: “There is no link for the moment between the vaccine and thrombolytic events with thrombocytopenia.
“There are a number of committees and regulatory authorities looking at data and new data is coming every day and [they are] assessing those data.
“Of course it’s under evaluation and we wait for some feedback from those committees in coming days and hours.
“The appraisal that we have for the moment, and this is under consideration by the experts, is that the benefit-risk assessment for the vaccine is still largely positive.”
He added: “For the time being there is no evidence that the benefit-risk assessment for the vaccine needs to be changed and we know from the data coming from countries like the UK and others that the benefits are really important in terms of reduction of the mortality of populations that are being vaccinated.”
Meanwhile he announced that the WHO will convene its Global Advisory Committee on Vaccine Safety to examine the data.
“So we expect that probably by the end of Wednesday or Thursday we might have a fresh conclusive assessment from our experts,” he added.
“But at the present moment we are confident that the benefits risk assessment for the vaccine is largely still positive.”
The EMA has previously said that there is “no evidence” to support restricting the use of the Oxford/AstraZeneca Covid-19 vaccine in any population.
But it will publish the findings from its safety committee either on Wednesday or Thursday.
The British regulator – the Medicines and Healthcare products Regulatory Agency (MHRA) – is also investigating reports of a very rare and specific type of blood clot in the brain, known as cerebral venous sinus thrombosis (CVST), occurring together with low levels of platelets (thrombocytopenia) following vaccination.
It has not confirmed when it will report its findings.
A number of countries have suspended the use of the jab among younger people.
The MHRA has said 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.
There have been seven deaths among the 30 cases.
But the regulator said the benefits of the vaccine in preventing coronavirus outweigh any risks and it urged the public to continue coming forward for the jab.
MHRA chief executive Dr June Raine said: “People should continue to get their vaccine when invited to do so.
“Our thorough and detailed review is ongoing into reports of very rare and specific types of blood clots with low platelets following the Covid-19 vaccine AstraZeneca.
“No decision has yet been made on any regulatory action.”
The 30 cases in the UK include 22 reports of CVST and eight of other thrombosis events with low platelets.
CVST clots stop blood draining from the brain properly.