You're reading: Wall Street Journal: Blood expert says he found why some Covid-19 vaccines trigger rare clots

Wall Street Journal: Blood expert says he found why some Covid-19 vaccines trigger rare clots

By Wall Street Journal.

Published May 14, 2021. Updated May 14 at 3:57 am

(FILES) In this file photograph taken on March 25, 2021, bottles of the single-dose Johnson & Johnson Janssen Covid-19 vaccine await transfer into syringes for administering at a vaccine rollout targetting immingrants and the undocumented in Los Angeles. - Europe's medicines regulator said April 20, 2021, that blood clots should be listed as a "very rare" side effect of Johnson & Johnson's coronavirus vaccine, but that the benefits of the shot still outweigh the risks. The United States is also expected to announce its decision on the single-shot J&J vaccine by April 23, as nations around the world urgently try to accelerate inoculation campaigns and revive their pandemic-ravaged economies. (Photo by Frederic J. BROWN / AFP)

Photo by AFP

Scientists world-wide are racing to understand why Covid-19 vaccines from AstraZeneca PLC and Johnson & Johnson are causing rare but potentially deadly blood clots. Determining the connection would help patients, doctors and health agencies better assess any risks posed by the vaccines and safely calibrate their use.