J&J, Astra viral vector vaccines paused
April 14, 2021 - After reports of rare blood clotting, the U.S., EU and South Africa have paused the rollout of Johnson & Johnson’s coronavirus vaccine. The move follows similar cases after doses of AstraZeneca’s vaccine.
With both the AstraZeneca and Johnson & Johnson (J&J)vaccines, the reports involve extremely rare clotting, including a type of blood clot called cerebral venous sinus thrombosis (CVST) combined with low levels of blood platelets.
As of April 4, the European Medicines Agency (EMA) has said it had received 169 reports of cases of CVST and 53 instances of splanchnic vein thrombosis (SVT), or clotting in veins in the abdomen. That’s out of 34 million AstraZeneca vaccine doses administered in Britain and the European Economic Area (EU, Iceland, Norway and Liechtenstein) over the past three months.
Most of the cases reported were in women under 60 years of age within two weeks of vaccination.
In the U.S., the Centers for Disease Control (CDC) and Food and Drug Administration (FDA) have data involving six reported cases of CVST out of more than 6.8 million single-shot J&J vaccine shots.
The CDC and FDA have recommended the suspension of the J&J vaccine “out of an abundance of caution.” South Africa has also suspended the rollout of the J&J vaccine after U.S. recommendations.
Both vaccines use “viral vector” technology. A common cold-causing adenovirus -- modified so it can’t replicate -- carries genetic instructions into human cells.
The gene creates a viral protein that stimulates the human immune system to produce antibodies. If infected, the antibodies attack the coronavirus, blocking its entry into cells where it can replicate.
AstraZeneca opted for a chimpanzee adenovirus, while J&J picked a human adenovirus. Experts suspect the adenovirus component may trigger rare cases of CVST.