On April 19, the CDC and FDA were made aware of 15 cases of a rare clotting disorder associated with the Johnson&Johnson vaccine, all of them in women. The number of cases has risen to 28, including six men.
Now, with the J&J vaccine back on the market, officials are saying that women between the ages of 30 and 49 are most at risk, while the overall risk of blood clots is still quite small, citing the more than 9 million doses of the vaccine that have been administered in the US.
Patients with the rare but serious disorder develop both blood clots, often in the brain, and low levels of platelets, blood components that promote clotting. The disorder is a “rare, clinically serious and potentially life-threatening condition,” says Dr. Tom Shimabukuro, the deputy director of the immunization safety office at the CDC, reports the New York Times.
The CDC is saying that of the 28 confirmed cases of patients with the clotting disorder, 12 people had obesity, 7 had high blood pressure, while 3 had diabetes, and three were taking estrogen. However, it is not clear if any of these factors played any role in the development of the clotting disorder.
Dr. Shimabukuro did note that no confirmed cases of clotting disorders have been seen with the Pfizer-BioNTech or Moderna vaccines, which use a different technology.
This could be what’s causing blood clots
Dr. Andreas Greinacher is a German physician who specializes in transfusion medicine and hemostasis. His scientific career is focused on platelet disorders, bridging immuno-hematology and hemostasis.
Greinacher, along with his team at the University of Greifswald, published a study on April 9 in The New England Journal of Medicine.
The team proposed that viral vector vaccines, which use modified viruses to transfer genetic material via vaccination, could result in an autoimmune response that provokes blood clots. Both the J&J and AstraZeneca vaccines are viral vector vaccines.
Dr. Greinacher and his colleagues have also done research on the AstraZeneca vaccine that suggests that EDTA, a preservative, causes proteins in the vaccine liquid to leak into the bloodstream and activate platelets by bumping into them.
Pharmaceutical Technology reports that with the AstraZeneca vaccine:
- EDTA increases the amount of vaccine proteins that leak from muscle into blood;
- Proteins from the vaccine interact with naturally-circulating platelets to form clumps, activating the platelets;
- Platelet activation releases another protein (platelet factor 4 or PL4) which sticks to proteins from the vaccine, including virus fragments;
- The presence of PL4 and proteins in the blood triggers the release of antibodies from the immune system;
- Large numbers of anti-PL4 antibodies trigger a larger immune response, parts of which may be inflammation (swelling) and increased blood clotting in some people.
With the Johnson&Johnson vaccine, the study concluded that the EDTA helps proteins from human cells stray into the bloodstream—once there, they bind to a blood component called platelet factor four (PF4). The inflammation that can come from the vaccine, combined with PF4, could confuse the immune system.
This can result in the rare development of immune thrombotic thrombocytopenia mediated by platelet-activating antibodies against PF4, which clinically mimics autoimmune heparin-induced thrombocytopenia.
