A group of German scientists claim they have worked out why the rare thrombosis with thrombocytopenia syndrome occurs in some people inoculated with AstraZeneca’s COVID-19 vaccine.

The researchers, led by Professor Rolf Marschalek at Goethe University in Frankfurt, suggest their discovery could help manufacturers of the viral-vector vaccines, including Johnson and Johnson, to “tweak” their products to eliminate the threat.

To date, hundreds of thrombosis with thrombocytopenia syndrome (TTS) events have been reported worldwide, including 27 cases in Australia.

The potential cause of the syndrome floated by the German team is that the immune system could be reacting to the adenovirus vector used in the vaccine.