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Concern of blood clot issues with the AstraZeneca and J&J vaccines

April 23, 2021  •  Blog  •  Kevin J. Gilligan Ph.D., Senior Consultant
Posted In Biologics News & Insights – Biologics Consulting  •  Tagged COVID-19 – Biologics Consulting – Blog, FDA, blood clots, coronavirus, EMA, serious adverse events, vaccines

The articles linked above describe a rare serious adverse event (SAE) observed and its possible association with AstraZeneca and Johnson & Johnson (J&J) COVID-19 vaccine inoculations. In a very small number of vaccine recipients, blood clotting occurred. Since both vaccines are based on an adenovirus-derived antigen expression platform, it raises questions about the safety of the vaccines and what the mechanism of action is for the reported vaccine-associated clotting events.

These clotting events are described as cerebral venous sinus thrombosis (CVST) and splanchnic vein thrombosis.  As of April 7, 2021, and pertaining to the Astra-Zeneca vaccine, 62 cases of CVST and 24 cases of splanchnic vein thrombosis, were observed, which included 18 deaths. A high proportion of the SAEs occurred in women.  The reports are derived from a European Union (EU) safety database. The SAEs reported were from among 25 million recipients of the vaccine. Most occurred in women within two weeks of receiving the first dose. Six cases of CVST were observed in J&J vaccine recipients, of which one (1) died.  All six CVST cases were women between the ages of 18 and 48.

As a precaution, regulatory authorities in various jurisdictions of the EU including the European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA) have put on hold further use of the vaccines, pending further risk assessment.  Studies are underway to assess immediate and long-term risks associated with the use of these vaccines.

The decisions to suspend use of and inoculation of these vaccines have had the effect of slowing the global vaccine campaign initiatives and placed a greater burden and responsibility onto other vaccine manufacturers to ramp up production to replace the resulting gap in vaccine supply.  In response to reported adverse event findings, a full risk/benefit assessment and consideration of resumption of use is warranted.