London — Vaccinations of children in a study of the Covid-19 shot developed by AstraZeneca  and the University of Oxford have been paused while the UK’s drug regulator investigates rare cases of blood clots in adults.

The vaccine researchers are awaiting the results of a review by the Medicines and Healthcare Products Regulatory Agency, the UK’s drug watchdog, “before further vaccinations”, the university said in an e-mailed statement. No safety issues have arisen in the children’s trial, Oxford said.

The action comes after a growing number of reports of rare brain blood clots in younger adults have led some countries, including several in the EU, to suspend use of the vaccine in certain age groups. Germany halted use of the AstraZeneca vaccine for people younger than 60 last week, while Canada has limited its use to those more than 55 years old.

Drug regulators in the UK and EU have said that a connection between the clots and the vaccine is possible but unclear, and that the benefits continue to outweigh the risks. An update from the European Medicines Agency (EMA) planned this week may indicate a potential link between the drugmaker’s shot and the blood clots, Italian newspaper Il Messaggero reported on Tuesday, quoting Marco Cavaleri, chair of the EMA’s vaccine evaluation team.

US trial planned

Cavaleri’s comments were personal and preliminary, the drug regulator said in an e-mailed statement. The EMA referred to a March 31 statement in which it said it would issue an updated recommendation on the issue during its plenary meeting that takes place this week. The agency said this will most likely happen April 7.

The UK’s regulator said on Saturday that it had identified 30 cases of a rare combination of blood clots and low platelets in people in Britain who had received the AstraZeneca shot through to March 24, of whom seven died.

The Oxford trial plans to enrol 300 children and adolescents aged 6 to 17, the university said when it began the study in February. As many as 240 participants would receive the coronavirus vaccine and the remainder a meningitis shot. Initial data from the trial is expected by the summer, Oxford said at the time.

AstraZeneca is planning to start a larger US trial for children, similar to those run by Pfizer and Moderna, in the coming months.

Parents and children continue to attend all scheduled visits and can contact the trial sites if they have any questions, the university said in the statement. The Wall Street Journal reported the pause in the study earlier.


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