A statewide analysis found that after receiving a first dose of a COVID-19 vaccine, people who acquired COVID within 21 days post-vaccination had an increased risk of ischemic and hemorrhagic stroke.
Although all the available vaccines for COVID-19 are considered safe and effective, rare vaccine-related thrombotic events have occurred.
For example, the CDC and FDA paused Janssen’s COVID-19 vaccine (Ad26.COV2.S) in 2021 due to an increased risk of a rare blood clot. The agencies removed that pause but recommended that people choose from the other available vaccines in most situations.
In addition, the CDC and FDA recently announced they observed a safety signal for the Pfizer-BioNTech COVID booster regarding a possible stroke risk in people 65 years and older within 21 days after receiving the vaccine.
In a new statewide retrospective cohort study, scientists examined the incidence of stroke in 5 million Georgia residents within 21 days after receiving the first dose of one of three available COVID-19 vaccines from December 2020 to February 2022.
The preprint study was posted on medRxiv and has not been peer-reviewed.
To evaluate the risk of stroke by vaccine type, the team linked data from the Georgia Immunization Registry with the Georgia Coverdell Acute Stroke Registry and the Georgia State Electronic Notifiable Disease Surveillance System.
Among the vaccinated residents, 54% received the Pfizer BioNTech BNT162b2 vaccine, 41% had Moderna’s mRNA-1273 vaccine, and 5% received Janssen’s Ad26.COV2.S shot. Moreover, approximately 9% had COVID-19 before receiving the vaccine, and 0.4% were infected during the 21 days post-vaccination.
After analyzing the data, the scientists found the 21-day post-vaccination incidence of ischemic stroke was:
- 8.14 per 100,000 people (Pfizer BioNTech BNT162b2)
- 11.14 per 100,000 people (Moderna’s mRNA-1273)
- 10.48 per 100,000 people (Janssen’s Ad26.COV2.S)
After the scientists adjusted for age, race, sex, and COVID-19 status, they found the Janssen vaccine was associated with a 57% higher risk for ischemic stroke within 21 days of vaccination compared to the Pfizer BioNTech shot.
In addition, across all vaccine types, people who had COVID-19 within 21 days post-vaccination had the highest risk of early ischemic and hemorrhagic stroke.
The study authors suggest that because COVID-19 has been linked to an increased risk of stroke, and those strokes tend to be more severe, their findings indicate that having COVID carries a higher stroke risk than the vaccines alone.
Although the analysis pulled data from large registries and linked to statewide vaccination date and type, statewide stroke diagnoses, and COVID-19 test results, it still had some limitations.
For example, the researchers did not have data on other health conditions contributing to stroke risk in vaccinated residents. In addition, the use of home COVID-19 tests may have resulted in underreporting of COVID-19 cases which could have affected the study results.