PT Jyothi Datta In the last two days, two regulatory authorities and the World Health Organization have weighed in on the benefits of the AstraZeneca-OxfordUniversity Covid-19 vaccine.

The United Kingdom’s Medicines Health Regulatory Authority (MHRA) and the European Medicines Agency (EMA) have urged people to continue with their vaccinations, after a review of the AZ-Oxford vaccine, following reports of blood clots in the recipients. The MHRA and EMA go-ahead came a day after the WHO said the benefits of taking the vaccine outweighed the risks.

Over 10 countries, mostly in Europe had suspended the use of the vaccine after the blood clot incidents. While most of them were reinstating the vaccine, some countries including Norway, Sweden and Denmark said they would further review the incidents in their respective countries before taking a call on revoking the suspension. India’s Serum Institute makes and markets this vaccine in low and middle income countries, besides others with whom it has contracts. India did not pause its vaccination using this vaccine.

Dr Swapneil Parikh pointed out that health interventions needed to be contextualised and this vaccine was a safe tool in combating the worst pandemic in a century. Dr Parkih is the co-author of ‘The Coronavirus : What you need to know about the global pandemic’.

The learning from these incidents, he said, was that India’s adverse event related surveillance needed to be more robust, in terms of seeking them out, investigating deaths and sharing reports more transparently.

Rare clots being studied

The MHRA said in a statement that a rigorous scientific review of all available data did not show evidence to suggest that blood clots in veins (venous thromboembolism) were caused by AZ’s vaccine.

However, a detailed review into five UK reports of a very rare and specific type of blood clot in the cerebral veins (sinus vein thrombosis) occurring together with lowered platelets (thrombocytopenia) is ongoing, the regulator said. “This has been reported in less than 1 in a million people vaccinated so far in the UK, and can also occur naturally – a causal association with the vaccine has not been established,” it added.

The EMA’s Pharmacovigilance Risk Assessment Committee (PRAC) also cleared the vaccine’s links to an increased risk of clotting. However, it pointed out, “The vaccine may be associated with very rare cases of blood clots associated with thrombocytopenia, ie low levels of blood platelets (elements in the blood that help it to clot) with or without bleeding, including rare cases of clots in the vessels draining blood from the brain (CVST).” It added, “A causal link with the vaccine is not proven, but is possible and deserves further analysis.” The PRAC involved experts in blood disorders in its review, and worked closely with other health authorities including the UK’s MHRA which has experience with administration of this vaccine to around 11 million people. Overall the number of thromboembolic events reported after vaccination was lower than that expected in the general population, the EMA said. And this allowed the PRAC to confirm that there is no increase in overall risk of blood clots, it said, adding however that some concerns remained in younger patients, related in particular to these rare cases.

The EMA clarified that there was no evidence of problems related to specific batches of the vaccine or to particular manufacturing sites. Meanwhile, AZ said it would implement the recommendations of the PRAC, including the update of the product information.