A trial of the Oxford-AstraZeneca coronavirus vaccine in children was paused yesterday as the Medicines and Healthcare products Regulatory Agency (MHRA) continued to investigate a possible link between the jab and rare blood clots in adults.
A University of Oxford spokesperson said that no problems had arisen within the trial itself, but that it would wait for the results of the MHRA review on rare cases of thrombosis and thrombocytopaenia before administering any more doses to children. They added that parents and children should continue to attend all scheduled visits “and can contact the trial sites if they have any questions”.
Earlier yesterday, Boris Johnson defended the AstraZeneca vaccine during a visit to the pharmaceutical giant’s manufacturing plant in Macclesfield. The prime minister praised the work of the MHRA, but said that when it came to the vaccine, the advice was “to keep going out there – get your jab, get your second jab”.
Speaking to The Independent, Dr Simon Clarke, associate professor in cellular microbiology at the University of Reading, said the UK could “afford to be cautious” in pausing a trial of the Oxford-AstraZeneca vaccine in children, because it has access to other jabs.
“The whole story behind the increased blood clotting is quite opaque. And I still think they don’t really have a good idea about how common this is in the general population,” he said, adding that if a link is found between a certain age group and blood clots, then “there are other options … It’s not like it’s the only vaccine we’ve got.”
A senior official at the European Medicines Agency (EMA) said he believed that there was an association between the AstraZeneca vaccine and extremely rare cases of blood clots reported in people who had recently had the jab. In an interview with Italy’s Il Messaggero newspaper, Marco Cavaleri, head of vaccines strategy at the EMA, said it was “clear there is a link with the vaccine” but that there was still uncertainty about what exactly was causing such a reaction.
Mr Cavaleri said that among younger vaccinated people there was a higher than expected number of cases of cerebral thrombosis – blood clotting in the brain – compared with the general population.
A spokesperson for the EMA told The Independent that the Pharmacovigilance Risk Assessment Committee, which is reviewing the data, had “not yet reached a conclusion and the review is currently ongoing”, with an announcement expected today or on Thursday.
Europe’s regulator insisted as recently as last week that the “causal link with the vaccine is not proven” and has continued to recommend that people take the opportunity to get vaccinated when it is offered. Some countries, including Germany, France and Canada, have paused or restricted use of the vaccine in certain groups.
The World Health Organisation has said the benefits outweigh the risks, while AstraZeneca said in March that its vaccine was found in a US trial to be 76 per cent effective in preventing symptomatic infections, and that studies did not indicate higher risks of clotting.
Mr Cavaleri said the EMA’s evaluation of the AstraZeneca vaccine was “far from over” and that it was for individual countries to establish specific guidelines around which age groups were given which vaccines. However, he added: “In my opinion, we can now say it is clear there is a link with the vaccine. What causes this reaction, however, we still do not know.”
Additional reporting by Tom Batchelor