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Severe COVID-19 has led to a higher rate of cerebral venous sinus thrombosis (CVST) than COVID-19 vaccination, a study affirmed.

The Johnson & Johnson COVID-19 vaccine had a CVST rate of 0.9 per million (99% CI 0.2-2.3 per million) as of April 13, 2021, when the CDC reported six cases out of 6.85 million vaccinated people.

The similar adenovirus-based AstraZeneca vaccine had a rate of 3.6 per million (99% CI 2.7-4.8 per million) by that time in data from the U.K. where it is approved for use, with 77 cases out of 21.2 million vaccinated, Behnood Bikdeli, MD, of Brigham and Women's Hospital and Harvard Medical School in Boston, and colleagues reported in the Journal of the American College of Cardiology.

By comparison, background rate in the general U.S. population was 2.4 per million (99% CI 2.1-2.6 per million) based on the Nationwide Inpatient Sample for the months of March and April in 2018, the most recent year on record.

Notably, hospitalized COVID-19 patients had CVST at a rate of 207.1 per million (99% CI 23.3-757.7 per million), with three cases out of 14,483 patients in the Society of Vascular Interventional Neurology's COVID-19 registry.

A of 59 mainly U.S. healthcare organizations' electronic health records determined a somewhat lower cerebral vein thrombosis incidence (CVT, 42.8 per million) in the 2 weeks after COVID-19 diagnosis when pooling both hospitalized and non-hospitalized patients.

The CVT rate with the Pfizer and Moderna vaccines in that study was "compatible with even the lowest estimate of the baseline rate in the USA of 0.53 per million people in any 2-week period," that Oxford University group noted.

Bikdeli's study didn't have data on those mRNA vaccines. However, both groups cautioned about apples-to-oranges comparisons from different data sources and an evolving situation with small numbers of cases.

On June 3, U.K. regulators to 128 cases of CVST and 348 total cases of major thromboembolic events with concurrent thrombocytopenia out of 24.3 million vaccinated with at least one dose of the AstraZeneca shot.

The exact point estimates will change as the case numbers are updated, Bikdeli told 乌鸦传媒, but the data, despite their limitations, "give us hint of where we are, and it seems like the events are not dramatically off from the population."

"However, in sharp contrast, the proportion of people hospitalized with COVID-19 who develop cerebral vein thrombosis is much higher -- an order of magnitude," he added. "That piece of information in and of itself is valuable to patients, physicians, and policy makers."

CVST has not been well studied, so data like these are "a starting point," agreed Mary Cushman, MD, of the University of Vermont in Burlington.

"This spells out what we've all been saying, that these events are much less common after the vaccine than thrombosis events are after COVID, because COVID causes thrombosis," she told 乌鸦传媒. "The bottom line is the risk-benefit continues to be clearly in favor of being vaccinated."

Her group's from the American Heart Association released in April on diagnosis and management of CVST with vaccine-induced thrombotic thrombocytopenia (VITT) pointed out that the stakes are high.

"There is a considerable risk to patients if scientific data are taken out of context, and without appropriate caveats," that report said, citing concerns of how CVST and VITT reporting would impact vaccine hesitancy.

Updated analyses should be possible in a few more months, and it's likely that the CDC and FDA will report out pooled data that provide further clarity about risk as well, Bikdeli said.

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