The University of Oxford has halted administering doses of the Covid-19 vaccine it developed with AstraZeneca to children, pending further information about rare blood-clotting issues in adults who have received it.
The trial of the Oxford/AstraZeneca Covid-19 vaccine on children, aimed at assessing whether the jab produces a strong immune response in those aged between six and 17, started mid February.
Confirming that the trial was paused, Prof Andrew Pollard, from the University of Oxford, said: "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."
Prof Pollard told the BBC there were no safety concerns with the trial itself, but that its scientists were awaiting further information.
The university is waiting for more information from the UK’s drugs regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), before giving any further vaccinations to children or teenagers in the pediatric trial.
The pause is the latest setback for the Oxford/AstraZeneca shot, which has faced questions about its efficacy and potential side effects, with millions of doses administered in about 78 countries.
Concerns about rare but serious blood clotting events in a small number of recipients have plagued the shot in recent weeks. More than a dozen European countries briefly suspended its use last month pending an investigation by Europe’s drug regulator, the European Medicines Agency (EMA).
Reported deaths have been linked to unusual blood clots in the brain, known as cerebral venous sinus thrombosis (CVST), accompanied by a low platelet count.
A high proportion among the reported cases were young and middle-aged women.
In the UK, the MHRA also reported 22 cases of CVST as well as eight reports of other blood clotting problems with low platelets, up to and including March 24. Out of 30 reports, the agency said seven people had died.
In a statement to Agence France-Presse, EMA, which is looking into 14 deaths among recipients of the jab, said on Tuesday it had “not yet reached a conclusion and the review is currently ongoing”, adding that it expected to announce its findings on Wednesday or Thursday.
Subsequently, the regulator said the vaccine was safe and effective, but added that it could not definitively rule out a connection between the jab and the rare clotting events, and so was continuing to investigate.
The World Health Organization (WHO), EMA and MHRA have all said people should continue taking the vaccine because the benefits in preventing Covid-19 infection and its complications far outweigh any risks.
The AfricaCDC has continued to advocate its use, saying the benefits outweigh the risks.
Director of the continent’s public health agency, John Nkengasong, said the benefits outweigh the risks, and that the Africa CDC recommends the continued use of the vaccine in the continent.
Most countries have since resumed inoculation with the AstraZeneca shot, but several – including France, Germany, Italy, France, Spain, the Netherlands, and Canada – have suspended its administration in people aged under 55, 60, or 65.
As several European countries suspend their rollout of the Oxford/AstraZeneca vaccine, many African countries are continuing with it, as a principal jab.
In Uganda and Nigeria, health authorities believe the vaccine is safe.
In Kenya, an estimated 300,000 people have so far received their first shot of the AstraZeneca vaccine.
Kenya's Ministry of Health has not commented on the matter of blood clots though immunisation data so far indicates that the Pharmacy and Poisons Board (PPB) has recorded at least 277 cases of notable reactions to the vaccine.
In its statement on the pandemic on Tuesday, the ministry only mentioned headaches as among the effects and said they clear within two days.
It did not mention other exact reactions, only saying that the drug regulator was investigating seven cases.
"We have not recorded any cases of severe reaction or death due to the vaccine. We have also not recorded any cases of blood clots," said Dr Collins Tabu, head of Kenya's National Vaccines and Immunization Programme.
The Democratic Republic of Congo is the only African nation to postpone the start of its AstraZeneca vaccination campaign over blood clot fears.