health
February 12, 2026
Scientists Figured Out the Problem With Johnson & Johnson’s COVID Vaccine
Rare but dangerous blood clotting associated with that vaccine as well as AstraZeneca’s had a genetic cause, according to a new paper.
TL;DR
- Rare blood clotting events (VITT) were linked to Johnson & Johnson and AstraZeneca COVID-19 vaccines.
- Researchers discovered that VITT was caused by an immune system overreaction to the adenovirus vector used in these vaccines.
- Individuals genetically prone to VITT had specific DNA variants that, combined with a chance mutation, led to the production of antibodies targeting a blood clotting factor (PF4).
- This discovery explains the rarity of VITT and can help in designing safer adenovirus-based vaccines by modifying problematic protein regions.
- The findings may also shed light on why viral infections can sometimes cause dangerous blood clotting.
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