Video report by ITV News Science Editor Tom Clarke
The trial of the Oxford/AstraZeneca Covid-19 vaccine in children has been paused while regulators investigate a potential association between the jab and a rare form of blood clot.
The University of Oxford said that no safety concerns have arisen from the trial itself.
However, it is waiting for more information from the Medicines and Healthcare products Regulatory Agency (MHRA) before giving any more vaccinations.
A spokesperson from the University of Oxford said in a statement: “Whilst there are no safety concerns in the paediatric clinical trial, we await additional information from the MHRA on its review of rare cases of thrombosis/thrombocytopaenia that have been reported in adults, before giving any further vaccinations in the trial.
Tom Clarke discusses latest updates on AstraZeneca vaccine
“Parents and children should continue to attend all scheduled visits and can contact the trial sites if they have any questions.”
Regulatory bodies from the UK, Europe and the World Health Organisation (WHO) are assessing data on the jab and a potential association with the clots.
WHO and the European Medicines Agency (EMA) have confirmed they will publish findings later this week, while the MRHA has not confirmed when it will report back.
The investigations regard 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.
UK Prime Minister Boris Johnson has urged people to get their vaccine when invited, despite concerns being raised about the Oxford/AstraZeneca jab.
He said getting the population vaccinated was “the key thing”.
“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”.
Sage adviser Professor Calum Semple urged people to continue accepting Oxford/AstraZeneca jabs despite the children's trial being paused.
He said: “This has been done out of exceptional caution and the big story still is that for a middle-aged, slightly overweight man, such as myself, my risk of death is one in 13,000.
"The risk of this rare clot, which might not even be associated with the vaccine, is probably one in a million. So I'm still going to say it is better to get the vaccine then not get the vaccine."
Dr Rogerio Pinto de Sa Gaspar, director of regulation and prequalification for WHO, said: “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.”
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.