Stroke, thrombosis remain rare after COVID-19 vaccination

Key takeaways:

• Stroke, thrombocytopenia and thrombosis occurred in fewer than 1% of patients 30 days after bivalent or monovalent COVID-19 vaccinations.
• The findings remain consistent with previous FDA and CDC research.

The incidence of stroke, thrombocytopenia and thrombosis were rare in patients following COVID-19 vaccination, while all three complications were more likely in patients who received an influenza vaccination, a report found.

In light of the findings, primary care physicians “should continue to recommend that their patients follow CDC guidelines when receiving the COVID-19 vaccinations for which they are eligible,” Kersten Bartelt, RN, a clinician at Epic Research, a public benefit corporation that expedites data publication through internal peer review, told Healio.

Previously, “there have been some reports of ischemic stroke in patients after COVID-19 vaccination, but CDC and FDA have noted that these risks are small and continue to recommend COVID-19 vaccination for most patients,” Bartelt and colleagues wrote. “Additionally, there have been contradictory observations around the risk of stroke and thrombosis related to receiving the COVID-19 vaccination,” they added.

In January, health officials said a safety signal detected by a national surveillance system was “very unlikely” to represent a “true clinical risk” for stroke among older people who received the Pfizer-BioNTech bivalent COVID-19 booster. The CDC and FDA said they came to that conclusion after multiple analyses of other vaccine surveillance databases failed to validate the signal from the CDC’s Vaccine Safety Datalink, a near real-time surveillance system.

Still, as both the monovalent and bivalent COVID-19 vaccinations “make use of pioneering mRNA design, we wanted to compare rates of different clotting conditions following COVID-19 mRNA vaccination with those following a non-mRNA vaccination, such as the influenza vaccine,” the researchers wrote.

To do this, Bartelt and colleagues evaluated 16,687,080 patients who had received an influenza vaccination, monovalent or bivalent COVID-19 vaccination, or a SARS-CoV-2 infection. Among the patients, 59.9% were women and 29.6% were aged 51 to 65 years.

Each patient group was then matched based on age, sex, immunization or infection year and prior diagnosed chronic conditions that increased cardiovascular risk.

Overall, stroke, thrombocytopenia and arterial and venous thrombosis were all uncommon 30 days after bivalent or monovalent COVID-19 vaccinations, with occurrences in fewer than 1% of patients.

Additionally, patients who received either COVID-19 vaccines were 9% less likely to develop a stroke, 20% less likely to develop thrombocytopenia and 12% less likely to develop thrombosis compared with patients who received the influenza vaccine.

“Both COVID-19 vaccinations were nearly equivalent for all four of the cardiovascular diagnoses assessed,” the researchers wrote.

The incidence of thrombocytopenia (IR = 1.018%; 95% CI, 0.997-1.039) and thrombosis (IR = 1.165%; 95% CI, 1.143-1.188) were also found to be twice as common following a SARS-CoV-2 infection than after receiving a COVID-19 vaccination.

“What surprised me the most was how much greater the risk of stroke, thrombosis and thrombocytopenia were after COVID-19 infection than after COVID-19 vaccination,” Bartelt said.

The researchers concluded that the “findings align with CDC and FDA reports that these conditions after COVID-19 vaccination remain rare and suggest that bivalent and monovalent COVID-19 vaccinations have similar rates of these diagnoses after vaccination.”

References:

• CDC & FDA identify preliminary COVID-19 vaccine safety signal for persons aged 65 years and older. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/bivalent-boosters.html. Published Jan. 13, 2023. Accessed June 1, 2023.
• Stroke and blood clotting disorders rare after monovalent and bivalent COVID vaccination. https://epicresearch.org/articles/stroke-and-blood-clotting-disorders-rare-after-monovalent-and-bivalent-covid-vaccination. Published May 24, 2023. Accessed May 31, 2023.