CDC-Funded Study of Nearly 100 Million COVID-19 Vaccine Recipients Reveals a Host of Adverse Events

Cases of a blood clot condition called CVST were found to be three times higher than expected among the vaccinated.

A health care worker fills a syringe with Pfizer's COVID-19 vaccine in a file image. Robyn Beck/AFP via Getty Images

A multinational study of over 99 million vaccinated people has identified higher incidences of neurological, cardiovascular, and blood disorder complications than what the researchers expected.

The peer-reviewed observational cohort study, published in the Vaccine journal on Feb. 12, aimed to evaluate the risk of 13 adverse events of special interest (AESI) following COVID-19 vaccination. The AESIs spanned three categories—neurological, hematologic (blood), and cardiovascular.