The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has concluded that there is a possible link between AstraZeneca’s COVID-19 vaccine and “extremely rare, unlikely to occur blood clots”.

In a statement, the regulator said the benefits of vaccination continue to outweigh any risks but it advised that careful consideration be given to people at higher risk of specific types of blood clots because of their medical condition.

Up to and including March 31, the MHRA had received 79 UK reports of blood clotting cases alongside low levels of platelets following the use of AZ’ vaccine, which all occurred after the first dose. Nineteen people died as a result, of which 13 were females and six males.

Eleven out of the 19 who died were under the age of 50, three of whom were under 30. Fourteen of these 19 cases were of cerebral venous sinus thrombosis (CVST) with thrombocytopenia and five were of thrombosis with thrombocytopenia.

By March 31, 20.2 million doses of AZ’ COVID-19 vaccine had been given in the UK, putting the overall risk of these blood clots at around four people in a million who receive the vaccine, according to the regulator.

The data suggests a slightly higher incidence reported in the younger adult age groups and so the MHRA advises that this evolving evidence should be taken into account when considering the use of the vaccine. As such, the government has said that anyone aged under 30 will be offered an alternative vaccine if one is available.

“The key message to take away from both the EU and the UK regulators is that the benefits of the AstraZeneca vaccine still outweigh any potential risks and we hope the public will be reassured that a thorough review has been undertaken and the necessary precautions taken,” said Ruth Rankine.

The UK has begun rolling out Moderna’s coronavirus vaccine, following its regulatory approval back in January.

The government has ordered 17 million doses of the jab, an mRNA vaccine given in two doses between four and 12 weeks apart.

Efficacy analysis of the Phase III COVE study, which involved 30,000 participants, indicates that the vaccine is 94% effective against COVID-19 and 100% effective against severe disease.

Also, no serious safety concerns have been identified to date, and a study recently published in the New England Journal of Medicine indicates that it offers protection against COVID-19 for at least six months

The European Medicines Agency (EMA) has launched a review of GlaxoSmithKline and Vir Biotechnology’s investigational dual-action monoclonal antibody (mAb) VIR-7831 for the early treatment of COVID-19.

According to GSK, the review will include an interim analysis of efficacy and safety data from the Phase III COMET-ICE trial, which based on data from 583 randomised patients showed an 85% reduction in hospitalisation or death for those who received the mAb compared to placebo.

Following this result, the Independent Data Monitoring Committee recommended that enrolment into the trial be stopped, based on evidence of ‘profound efficacy’.

Preclinical data also suggests VIR-7831 targets a highly conserved epitope of the SARS-CoV-2 spike protein, potentially making it more difficult for resistance to build up, while new in vitro data also demonstrates that it maintains activity against currently circulating variants of concern – including those discovered in the UK, South Africa and Brazil.