Influenza vaccine effect on risk of stroke occurrence: a systematic review and meta-analysis

Jalal A Zahhar; Hassan K Salamatullah; Maher B Almutairi; Dania E Faidah; Lena M Afif; Toka A Banjar; Nayef Alansari; Manar Betar; Saeed Alghamdi; Seraj Makkawi

doi:10.3389/fneur.2023.1324677

Influenza vaccine effect on risk of stroke occurrence: a systematic review and meta-analysis

Front Neurol. 2024 Jan 10:14:1324677. doi: 10.3389/fneur.2023.1324677. eCollection 2023.

Authors

Jalal A Zahhar^#^{1

2}, Hassan K Salamatullah^#^{1

2}, Maher B Almutairi^{1

2}, Dania E Faidah^{1

2}, Lena M Afif^{1

2}, Toka A Banjar^{1

2}, Nayef Alansari^{1

2}, Manar Betar^{1

2}, Saeed Alghamdi³, Seraj Makkawi^{1

2

4}

Affiliations

¹ College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Jeddah, Saudi Arabia.
² King Abdullah International Medical Research Center, Jeddah, Saudi Arabia.
³ Neuroscience Department, King Faisal Specialist Hospital and Research Center, Jeddah, Saudi Arabia.
⁴ Department of Neurosciences, Ministry of the National Guard-Health Affairs, Jeddah, Saudi Arabia.

^# Contributed equally.

Abstract

Background: Stroke is a significant global cause of mortality and long-term disability, potentially influenced by infections that heighten systemic inflammation and thrombotic events. The full impact of influenza vaccination on stroke remains uncertain. This systematic review and meta-analysis aimed to investigate the association between influenza immunization and stroke incidence.

Methods: We searched for randomized controlled trials (RCTs), case-control, and cohort studies published in PubMed/Medline, Cochrane-Central-Register-of-Controlled-Trials (CENTRAL), and Embase until 5 December 2022, and identified articles investigating the effect of influenza vaccine on stroke occurrence. All articles were screened by two independent reviewers. We performed a meta-analysis to investigate the risk of stroke occurrence in vaccinated vs. unvaccinated individuals. The random-effects model was used in all statistical analyses.

Results: Among the 26 articles meeting our criteria, 10 were retrospective cohort studies, 9 were case-control studies, 3 were prospective cohort studies, 3 were RCTs and 1 case-series. Overall, the studies showed a significant decrease in the risk of stroke incidence/hospitalization among vaccinated patients (OR = 0.81, 95% CI [0.77-0.86], p = 0.00001). Furthermore, studies showed flu vaccine decreases the occurrence of mortality among stroke patients (OR = 0.50, 95% CI [0.37-0.68], p = 0.00001). Sub-group analysis revealed significant protective effect for patients with specific comorbidities including atrial fibrillation (OR = 0.68, 95% CI [0.57-0.81], p = 0.0001), diabetes (OR = 0.76, 95% CI [0.66-0.87], p = 0.0001), Chronic obstructive pulmonary disease (OR = 0.70, 95% CI [0.61-0.81], p = 0.00001), and hypertension (OR = 0.76, 95% CI [0.70-83], p = 0.00001).

Conclusion: The current meta-analysis further supports prior findings that influenza vaccination reduces stroke risk, particularly in patients with comorbidities. Guidelines should promote vaccination for at-risk individuals.

Keywords: acute cerebrovascular accident; hemorrhagic stroke; influenza vaccine; ischemic stroke; stroke occurrence.

Publication types

Systematic Review

Grants and funding

The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.