How concerning are links of blood clots to AstraZeneca's vaccine?

How worried should we be about links of blood clots to AstraZeneca's vaccine? Europe's drug regulator on Wednesday said it had found a possible link between AstraZeneca's COVID-19 vaccine and very rare blood clots in adults who received the shot. Britain recommended people under 30 get an alternative COVID-19 vaccine if possible. John Miller, Ludwig Burger U.S.

ZURICH (Reuters) - Europe’s drug regulator on Wednesday said it had found a possible link between AstraZeneca’s COVID-19 vaccine and very rare blood clots in adults who received the shot. Britain recommended people under 30 get an alternative COVID-19 vaccine if possible.

Here’s what we know so far:

The EMA said its vaccine side effects monitoring system, as of April 4, had received 169 reports of cases of cerebral venous sinus thrombosis (CVST), or clots in blood vessels exiting the brain, and 53 cases of splanchnic vein thrombosis (SVT), or clotting in veins in the abdomen.

That’s out of some 34 million AstraZeneca vaccine doses administered in Britain and the European Economic Area since vaccinations started almost three months ago.

Its safety committee carried out a review of 62 cases of CVST and 24 cases of SVT, of which 18 were fatal.

Most of the cases reported have occurred in women under 60, though that could be misleading. Germany and Britain say many more women received AstraZeneca’s shot than men.

German vaccination officials who recorded 29 cases of CVST in women aged 20 to 59 who got the AstraZeneca vaccine said the occurrence rate in that group was 20 times higher within 16 days of vaccination than what would have typically been expected.

Germany’s health ministry has said 1 to 1.4 cases of CVST would have been expected during that time. ...

Key to the EMA’s assessment that benefits continue to outweigh risks are its conclusions about likelihood of an increased risk from clotting, compared with the benefits of preventing COVID-19 and reducing hospitalizations and deaths. ...

The EMA said that unusual blood clots with low blood platelets should be listed as very rare side effects and countries should decide on how to proceed with their national COVID-19 immunisation campaigns.

These may vary from nation to nation, the EMA said, depending on factors like how quickly infections are spreading and whether vaccines are available. Its safety committee requested new studies, and changes to ongoing ones, to provide more information about the mechanism behind the rare clots. ...