CVST Risk Still Higher With COVID-19 Than With AZ, J&J Vaccination

June 10, 2021

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Another study has suggested that rates of cerebral venous sinus thrombosis (CVST) are much higher among patients with COVID-19 than among persons after they have been vaccinated with either the AstraZeneca or the Johnson & Johnson vaccine.

For the study, a group led by Behnood Bikdeli, MD, Brigham and Women's Hospital, Boston, Massachusetts, estimated on the basis of publicly reported data the rate of CVST associated with the two vaccines in comparison with the rate among patients hospitalized with COVID-19 and in comparison with the estimated incidence rates among the US population before the pandemic.

They used the data from the United Kingdom Medicines and Healthcare products regulatory agency and the US Centers for Disease Control and Prevention to report the number of events per vaccinated people with the AstraZeneca and Johnson & Johnson vaccines, respectively.

Rates of CVST among patients hospitalized with COVID-19 came from the SVIN COVID-19 multinational study of cerebrovascular events. Data from the Nationwide Inpatient Sample database (an all-payer database that includes approximately 20% of inpatient hospitalizations in the United States) from March and April 2018, the latest year for which information was available, were used to report the weighted monthly incidence of CVST before the pandemic.

Results showed that as of April 14, 2021, there were 77 CVST cases among 21,200,000 AstraZeneca vaccine recipients reported by the UK Medicines and Healthcare Products Regulatory Agency (3.6 per million; 99% CI, 2.7 – 4.8 per million).

As of April 13, 2021, the Centers for Disease Control and Prevention reported six cases of CVST among 6.85 million vaccinated people (0.9 per million; 99% CI, 0.2 – 2.3 per million).

In the SVIN COVID-19 registry, 3 of 14,483 patients hospitalized with COVID-19 had CVST (207.1 per million; 99% CI, 23.3 – 757.7 per million).

In the Nationwide Inpatient Sample, the weighted average rate of CVST in the US population for March and April 2018 was 2.4 per million (99% CI, 2.1 – 2.6 per million).

The authors conclude: "CVST is rare in the general population and after adenovirus-based SARS-CoV-2 vaccination, but appears to be several-fold more common in hospitalized patients with COVID-19.

"Additional research is required to fully elucidate the event rates, to understand the risk factors for vaccine-associated CVST and to identify strategies to prevent it. In the meantime, transparent realistic communication of the risk estimates will be helpful for shared decision making between patients and clinicians," they add.

The researchers report their findings in an article published online in the Journal of the American College of Cardiology on June 8.

Bikdeli acknowledged that rates of CVST among vaccinated persons have increased since his article was submitted for publication.

On May 26, in the United Kingdom, 348 cases of CVST were linked to 37.7 million doses of the AstraZeneca vaccine, a rate of around 1 in 100,000. A study conducted in Norway and Denmark estimated the actual rate to be nearer to 1 in 40,000.

"Yes, the numbers linked to the vaccine will change, and while the point estimates may be different ― it is better to look at the 99% CIs as an estimate ― and even if the point estimates change, the message is unlikely to change," Bikdeli told Medscape Medical News. "The risk of CVST is far higher with COVID-19 infection than with vaccination.

"The estimates for CVST after COVID-19 infection and after vaccination are so far apart, some changes in the numbers being reported will not make much difference," Bikdeli added.

A similar study by a group from the University of Oxford, Oxford, United Kingdom, estimated the risk for CVST among patients with COVID-19 (both hospitalized and nonhospitalized) using an electronic health records network that included anonymized data from 81 million patients from 59 healthcare organizations, primarily in the United States. That study is currently available only as a preprint.

Those investigators found that among 537,913 patients with a confirmed diagnosis of COVID-19, 23 were diagnosed with a CVST in the 2 weeks following their diagnosis, giving an absolute risk of 42.8 per million people (95% CI, 28.5 – 64.2), equivalent to an incidence of 111.5 per 100,000 person-years.

When the definition of CVST was broadened with respect to ICD-10 codes, the incidence increased to 148.7 per million people (95% CI, 119.5 – 185.1).

Bikdeli said it was not possible to compare rates of CVST in the two studies.

"The Oxford paper used different data sources, a different patient population (all infected patients rather than just those hospitalized) and methods and has not yet been peer reviewed. You cannot really compare such data," he commented.

He stressed that the focus should not be on the absolute event rates in these studies but rather on the magnitude of the differences between the vaccine and the rate after SARS-CoV-2 infection.

"However you look at it, the risk is much higher after COVID-19 infection than after vaccination," he said.

"There has been so much concern about CVST with the vaccines, but we need to understand the magnitude of this risk in context and relative to the risk associated with COVID infection. It is important to be able to make informed choices, and these data can help with that," Bikdeli added.

The study did not receive any commercial funding. Bikdeli is a consulting expert on behalf of the plaintiff for litigation related to two specific brand models of IVC filters.

J Am Coll Cardiol. Published online June 8, 2021. Abstract

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