Possible Cause Found for Rare Blood Clots Tied to Some COVID-19 Vaccines

The cause of rare blood clots in some people who have received the AstraZeneca and Johnson & Johnson COVID-19 vaccines has been found, researchers report.

The vaccines use adenovirus vectors to transfer the vaccine's components into cells, but some of the material slips into the nucleus of cells, which is not an ideal location for the virus to make proteins, the German scientists explained, The Washington Post reported. These inferior proteins, some of which may split apart inside the body, could trigger blood clots in a small number of people who receive the vaccines, according to the non-peer-reviewed study posted online.

COVID-19 vaccines that use mRNA technology, including Pfizer and Moderna, work in a different way and "should represent safe products," the study said.

Rolf Marschalek, one of the study's authors, told the Financial Times that adenovirus vector vaccines can be tweaked to eliminate the risk of blood clots, and said that Johnson & Johnson "is trying to optimize its vaccine now," The Post reported.