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

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

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 Alghamdi  3 , Seraj Makkawi  1   2   4
Affiliations

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

Jalal A Zahhar et al. Front Neurol. .

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.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of study selection.
Figure 2
Figure 2
Forest plot showing the effectiveness of influenza vaccine on stroke incidence/hospitalization. CI, confidence interval.
Figure 3
Figure 3
Funnel plot. OR, odds ratio.
Figure 4
Figure 4
Forest plot showing the effectiveness of influenza vaccine on mortality in stroke patients. CI, confidence interval.
Figure 5
Figure 5
Forest plot showing the effectiveness of influenza vaccine on stroke incidence/hospitalization by study design, stroke subtypes, prevention, and location. CI, confidence interval.
See this image and copyright information in PMC

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