Researchers from several universities have published findings on the mechanism behind the rare syndrome of vaccine-induced immune thrombocytopenia and thrombosis (VITT). The study was published on 12 February 2026 in The New England Journal of Medicine. The analysis covered documented cases of VITT observed after exposure to adenovirus-based vaccines and after natural adenovirus infection. The researchers found that the condition is associated with an immune response initially directed against the adenoviral protein pVII.
In rare cases, a specific somatic mutation in antibody genes caused the antibodies to bind to platelet factor 4 (PF4) instead of the viral antigen. This reactivity to PF4 leads to platelet activation and the formation of blood clots. The identified mutation was present in all analysed antibodies obtained from patients with VITT. Reverting the mutation to its original form removed the ability to induce clot formation.
The findings provide a molecular explanation for how a normal immune response to adenovirus can, in rare cases, shift towards autoimmunity targeting PF4.