COVID Vaccines Not Tied to Increased Risk for Stroke

Megan Brooks

August 31, 2022

COVID-19 vaccines do not raise the risk for acute arterial ischemic stroke (AIS), new research suggests.

Pooled data from a systematic review and meta-analysis showed that postvaccine AIS events were about 20 times less frequent than were strokes occurring in the general population and roughly 200 times less frequent than were strokes occurring in patients hospitalized with COVID.

The analysis "is the first to systematically approach the available-to-date literature on AIS following immunization with SARS-CoV-2 vaccines," the investigators, led by Maria-Ioanna Stefanou, MD, Attikon University Hospital, Athens, Greece, write.

Overall, the results "indicate that post-vaccination AIS is very uncommon," they add.

The findings were published online August 24 in Neurology.

Favorable Risk-Benefit Ratio

AIS has been reported as a rare adverse event after COVID-19 vaccination with mRNA or viral-vector vaccines. However, data are limited regarding the risk for postvaccination AIS, potentially resulting from thrombotic thrombocytopenia syndrome (TTS).

To investigate further, Stefanou and colleagues analyzed more than 782 million COVID vaccine exposures by pooling data from 11 registries, three cohort studies, two randomized controlled clinical trials, and 40 case reports.

Overall, 17,481 (.002%) of COVID vaccine exposures were associated with an AIS event.

After any COVID-19 vaccination, AIS events occurred at a rate of 4.7 per 100,000 vaccinations.

"Thus, even when comparing to conservative estimates of AIS of roughly 1% among hospitalized COVID-19 patients (corresponding to 1000 per 100,000 infections), the prevalence of AIS is about 200 times lower following COVID vaccination compared to the risk of AIS complicating moderate to severe COVID-19 infection," the investigators write.

They note that the pooled proportion of AIS tended to be higher after administration of mRNA-vaccines compared with adenovirus-vaccines (pooled prevalence, 9.2 vs 2.9 cases per 100,000 vaccinations, respectively). However, this difference was not statistically significant in sensitivity analyses accounting for the time between vaccine exposure and the event.

In addition, TTS was rare, occurring in only about 3% of the AIS events, and was not dependent on vaccine type. This suggested that TTS does not significantly predispose to AIS, the researchers note.

Summing up, they write that there is an "overwhelmingly favorable" risk-benefit ratio for SARS-CoV-2 vaccination because the prevalence of AIS occurring after vaccination is much lower relative to the prevalence of AIS complicating SARS-CoV-2 infection.

"Pivotal" Study

In an accompanying editorial, Alexis Simpkins, MD, PhD, and Susan Cheng, MD, both with Cedars-Sinai Medical Center, Los Angeles, California, note that the results of the meta-analysis "offer reassurance that the frequency of post-vaccine AIS is generally lower than the frequency of post-COVID AIS."

This "pivotal" study, Simpkins told Medscape Medical News, shows that vaccination may play "an important role not only in preventing severe COVID-19 but also in preventing acute arterial ischemic stroke in the general population, especially in patients with risk factors for stroke, cardiovascular disease, and severe COVID-19."

She added that patients and clinicians should continue to follow guidelines from the Centers for Disease Control and Prevention (CDC) for the most up-to-date recommendations.

"If there is any question regarding personalized risk associated with COVID-19 vaccination and acute arterial ischemic stroke, those concerns should be addressed with a patient-to-provider personalized discussion, incorporating the CDC guidelines," Simpkins said.

The study had no targeted funding. The investigators and Simpkins have reported no relevant financial relationships. Cheng is a consultant for Zogenix.

Neurology. Published online August 24, 2022. Abstract. Editorial

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