Johnson & JohnsonThe European Medicines Agency (EMA) announced that it is beginning a review of blood clots appearing in a handful of recipients of the Johnson & Johnson COVID-19 vaccine. 

EMA recently concluded that blood clots associated with low blood platelet levels were a “very rare” side effect of Vaxzevria, the vaccine from AstraZeneca. 

Four recipients of the Johnson & Johnson vaccine have had such blood clotting events. One of those individuals has died. 

A Johnson & Johnson summary of the Ad26.COV2.S vaccine clinical trial cited a “numerical imbalance” for deep vein thrombosis (DVT) and pulmonary embolism (PE) between vaccine and placebo recipients. In the vaccine arm, there were five cases of DVT and four cases of PE. By contrast, there were two DVT reports and one of PE in the study’s placebo arm. 

The company has stressed that it has found no causal relationship between the rare blood clotting events and its vaccine. 

European regulators have authorized the Johnson & Johnson vaccine but plan to administer it later this month. 

The Johnson & Johnson and AstraZeneca vaccines are both adenovirus-vectored. 

Within the Vaccine Adverse Event Reporting System, there are four reports of deep vein thrombosis and eight reports of pulmonary embolism among 25,204 of various vaccines from J&J’s Janssen unit.  

Separate teams of scientists in Germany and Norway have theorized that platelet factor 4 antibody could be linked to the blood clotting episodes in a small number of recipients of the vaccine from AstraZeneca, which is also known as ChAdOx1 nCov-19. “Vaccination with ChAdOx1 nCov-19 can result in the rare development of immune thrombotic thrombocytopenia mediated by platelet-activating antibodies against PF4, which clinically mimics autoimmune heparin-induced thrombocytopenia,’ the German group conclude in NEJM.

In related news, officials in Georgia paused vaccinations after eight people experienced adverse events after receiving the Johnson & Johnson vaccine. Several individuals in North Carolina and Georgia fainted after receiving the vaccine. 

Georgia health officials are investigating what caused the adverse events and are considering that the temperature of the mass-vaccination site may have played a role.