J&J COVID-19 Vaccine Linked to Increase in Rare Brain Blood Clots

The incidence of brain blood clots in one healthcare system increased by almost four times after introduction of the Johnson & Johnson (J&J) COVID-19 vaccine,  according to data published in the Nov. 1 issue of the Journal of the American Medical Association.

The postvaccination rate of cerebral venous sinus thrombosis (CVST)  was highest among women, who were five times more likely to develop a clot after vaccination than they were before the vaccine came along.

From 2001 to 2015, just 39 cases of the rare brain blood clot occurred in Olmstead County, Minn., Aneel A. Ashraimi and colleagues reported. This translates to an overall incidence rate of 2.34 cases per 100,000.  From February to May 2021, however, there were 38 cases, 27 of which (71 percent) occurred within 15 days of the patient receiving the J&J vaccine — an overall incidence rate of 8.65 per 100,000.

The risk was highest in the first two weeks, with an incidence rate of 13 per 100,000 person/years for women and 4.4 for men.

“In this population-based cohort study, we found that the CVST incidence rate at 15 days [postvaccination] was significantly higher than the prepandemic rate,” wrote Ashraimi and colleagues. “However, the higher rate of this rare adverse effect must be considered in the context of effectiveness of the vaccine in preventing COVID-19.” Vaccination  would have prevented 940 cases of severe or critical COVID-19 per 100,000 person/years, the team calculated.

Overall, women were significantly  more likely to develop the disorder than men (13 vs. 4.5 per 100,000 person/years). Women aged 40-49 years were at the greatest risk (29.5 cases per 100,000 person/years), followed by women aged 30-39 years (26.5 cases per 100,000 person/years). These were also the highest-risk groups in the prepandemic era.

“The reason that women had a higher incidence of postvaccination CVST is unclear,” the team wrote. “Concomitant CVST risk factors or autoantibody production might have been involved.”

In April, the FDA put a pause on J&J vaccination manufacturing after reviewing six postvaccination CVST cases. Later that month, the agency amended the vaccine’s Emergency Use Authorization to reflect the risk of rare blood clots and said vaccinations could resume, based on recommendations by a Centers for Disease Control and Prevention (CDC) advisory committee (DID, April 26).

Read the full study here: bit.ly/3nNqZQ. — Michele G. Sullivan