A number of European countries have suspended use of AstraZeneca’s COVID-19 vaccine over reports of dangerous blood clots in some recipients, though the company and international regulators say there is no evidence the shot is to blame.

Luis Schang is a molecular virologist who studies the interactions between viruses and cells, interactions which determine the outcomes of the infection and, consequently, pathogenicity. He says despite the concerns, this is likely the most careful worldwide vaccination campaign ever performed, and that suspending AstraZeneca vaccinations may lead to more blood clots — a common side effect of severe COVID-19.

Schang says:

“A number of countries have suspended the use of the AstraZeneca vaccine out of an excess of caution after a very limited number of consequential blood clots (deep vein thrombosis –DVT – and pulmonary embolism) were reported in some vaccinated patients. Through March 8 in the EU and the UK, 37 total cases were reported to AstraZeneca among 17 million vaccines, which is below the expected normal incidence of this types of thrombosis in the populations being vaccinated.

“The UK has applied 26.06 million doses of this vaccine to date without any reported increase in the frequency of these types of blood clots. The WHO and European Medicine Agencies (EMA), the EU regulatory agency, are meeting this week to perform an in-depth analysis of the reported cases, but in the meantime they both have expressed that they have found no evidence that the events were caused by the vaccine. 

“As a major concern, suspending vaccinations may result in an increase in total thrombosis cases. Thrombosis is common in serious COVID-19 cases, which is far more frequent in the susceptible populations being vaccinated than the reported frequency of blood clots among the vaccinated.

“The fact that this low frequency of a rare event was detected and reported and is being so thoroughly followed up constitutes an even further re-assurance that the SARS CoV-2/COVID-19 vaccination campaigns are proceeding with extreme caution and attention to even the most remote possibility of negative side effects. This may well be the most careful worldwide vaccination campaign ever performed.”


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