The study, published in The British Medical Journal (BMJ), also noted an increased risk following the Janssen/Johnson & Johnson vaccine compared to the Pfizer-BioNTech vaccine. The researchers noted that the syndrome is very rare, but added that the observed risks ‘should be considered when planning for further vaccination campaigns and future vaccine development.’
TTS differs from normal clotting conditions
TTS occurs when a person has a low blood platelet count (thrombocytopenia) along with a blood clot. According to the study, this is very rare and is different from common blood clotting conditions such as deep vein thrombosis (DVT) or lung clot. TTS is currently being investigated as a rare side effect of adenovirus-based COVID vaccines, which use a weakened virus to enhance the immune response against the coronavirus, but the study shows the comparative safety of different types of vaccines. But no clear evidence exists.
Events rare but may increase
To this end, an international team of researchers set out to compare the risk of a case of TTS or thromboembolic associated with the use of adenovirus-based COVID vaccines with mRNA-based COVID vaccines. “To our knowledge, this is the first multinational analysis of the comparative safety of adenoviruses compared to mRNA-based COVID-19 vaccines,” the study authors said. He cautioned that although these events are very rare, the number of affected patients could be significant due to the large number of vaccine doses around the world.