The Atlantic: "Scientists Figured Out the Problem With Johnson & Johnson's COVID Vaccine"
This is an important discovery...
"...because vaccines of this type could be essential in protecting people during future pandemics."
In 2021, just months after the first COVID vaccines debuted, concern was growing about an exceedingly rare but sometimes deadly outcome of certain shots. Two related vaccinesone from AstraZeneca and the other from Johnson & Johnsonwere linked to dangerous blood clotting.
Out of almost 19 million doses of Johnson & Johnsons version given in the United States during the first two years of the pandemic, at least 60 such cases were identified. Nine of them were fatal. In the United Kingdom, where almost 50 million doses of the AstraZeneca shot were given, 455 cases occurred; 81 people died. In Germany, at least 71 cases were identified, also linked to AstraZeneca. By late spring, use of both the AstraZeneca and the Johnson & Johnson vaccine was paused, and ultimately both were pulled from the market. But the mystery surrounding the rare blood clotting caused by these vaccines lingered.
...
The team that initially gave this condition a namevaccine-induced immune thrombotic thrombocytopenia, or VITTincluded Andreas Greinacher, a blood expert at the University of Greifswald, in Germany. Back in 2021, as the cases of VITT emerged, he and others were unsure of what precipitated them. One theory was that they were caused by the bodys accidental reaction to the type of virus used in both the AstraZeneca and Johnson & Johnson vaccines: adenoviruses, which had been engineered to prompt the body to recognize the pandemic coronavirus but were unable to replicate and considered harmless to people. Scientists had noticed that patients with VITT had telltale markers in their bloodantibodies that bind to a chemical signal released by platelets. Maybe a reaction to the adenovirus was causing immune cells to mistakenly go after a blood component and precipitate clotting. An alternative theory was that the body was reacting to a portion of the coronavirus called spike protein, which showed up as part of the immunization.
In a study published today in The New England Journal of Medicine, Greinacher and his colleagues show that the first theory was correct: VITT was a response to the adenovirus gone awry. And they discovered a further twist: This immune overreaction happened in people who were genetically prone to it.
https://www.theatlantic.com/science/2026/02/covid-vaccines-blood-clotting-answer/685966/
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