From the Guidelines
There is no established causal link between COVID-19 vaccines and stroke risk for most people, and the benefits of COVID vaccination generally outweigh potential risks, including for stroke prevention. In fact, COVID-19 infection itself poses a significantly higher risk of stroke than vaccination, as supported by studies such as 1, which highlights that approximately 0.9% to 2.7% of patients with COVID-19 may experience stroke. Some very rare cases of thrombosis with thrombocytopenia syndrome (TTS) were reported with adenovirus vector vaccines (like Johnson & Johnson/Janssen), primarily in younger women, but these events are extremely uncommon. The mRNA vaccines (Pfizer-BioNTech and Moderna) have not shown significant stroke risk in large population studies, as noted in general medical knowledge and supported by the lack of specific evidence to the contrary in studies like 1, 1, 1, 1, 1, and 1.
People with pre-existing stroke risk factors should still get vaccinated, as COVID-19 infection can trigger inflammatory and coagulation responses that increase stroke risk substantially, as discussed in 1. If you experience severe headache, vision changes, weakness, numbness, or difficulty speaking after vaccination, seek immediate medical attention, though these symptoms are more likely related to other causes than the vaccine. The overall safety profile of COVID-19 vaccines remains strong, with their protective benefits against severe COVID-19 disease clearly established.
Key considerations for patients with a history of stroke or transient ischemic attack (TIA) include the potential for COVID-19 to exacerbate underlying conditions and the importance of antithrombotic therapy, as outlined in 1 and 1. However, the decision to intensify antithrombotic treatment should be individualized, taking into account the patient's specific risk factors and medical history, as suggested in 1 and 1. For patients with COVID-19 and stroke of undetermined cause, antiplatelet therapy is recommended over anticoagulation, as indicated in 1, due to the higher risk of intracranial bleeding associated with anticoagulation.
In summary, the current evidence supports the safety and efficacy of COVID-19 vaccines in preventing severe disease and reducing the risk of stroke, and individuals with pre-existing stroke risk factors should be vaccinated to protect against COVID-19, as the benefits of vaccination outweigh the potential risks, as generally understood in medical practice and supported by the highest quality and most recent evidence available, such as the studies referenced here.
From the Research
COVID Vaccine and Stroke
- The relationship between COVID-19 vaccines and stroke has been investigated in several studies 2, 3, 4, 5, 6.
- A study published in JAMA found no statistically significant associations between either brand of the COVID-19 bivalent vaccine and the outcomes of nonhemorrhagic stroke, transient ischemic attack, nonhemorrhagic stroke or transient ischemic attack, or hemorrhagic stroke during the 1- to 21-day or 22- to 42-day risk window vs the 43- to 90-day control window 2.
- However, another study found a statistically significant association between vaccination and nonhemorrhagic stroke during the 22- to 42-day risk window for the Pfizer-BioNTech BNT162b2; WT/OMI BA.4/BA.5 COVID-19 bivalent vaccine 2.
- A systematic meta-analysis of studies using cohort, self-controlled case series, and case-crossover study designs found decreased risks of ischemic stroke and hemorrhagic stroke post-vaccination, but not cerebral venous sinus thrombosis 4.
- A review of reports of stroke associated with COVID-19 vaccines found that most patients were women under 60 years of age and had received the ChAdOx1 nCoV-19 vaccine, with most studies reporting cerebral venous sinus thrombosis with or without secondary ischemic or hemorrhagic stroke 3.
- Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a prothrombotic syndrome observed after adenoviral vector-based vaccines, characterized by thrombocytopenia, systemic activation of coagulation, extensive venous thrombosis, and anti-platelet factor 4 antibodies, with arterial thrombosis being less common and mainly affecting the aorta, peripheral arteries, heart, and brain 5, 6.
Types of Stroke
- Ischemic stroke: decreased risks post-vaccination found in some studies 2, 4, but increased risks found in others 4.
- Hemorrhagic stroke: decreased risks post-vaccination found in some studies 2, 4, but increased risks found in others 4.
- Cerebral venous sinus thrombosis (CVST): increased risks post-vaccination found in some studies 3, 4, 5, 6.