Individual and Joint Effects of Influenza-Like Illness and Vaccinations on Stroke in the Young: A Case-Control Study

Abstract

BACKGROUND: Influenza-like illness (ILI) is an acute trigger for stroke, although joint effects of vaccinations and ILI have not yet been explored. METHODS: Data for our case-control study was obtained from MarketScan Commercial Claims and Encounters between 2008 and 2014. Patients 18 to 65 years old who experienced a stroke were matched on age and admission date to a control, defined as patients with head trauma or ankle sprain at an inpatient or emergency department visit. Exposures were ILI in the prior 30 days, and any type of vaccination during the year prior. Our outcome was ischemic and intracerebral hemorrhagic strokes identified using International Classification of Diseases, Ninth Revision (ICD-9 ) codes. Logistic regression models estimated adjusted odds ratios (aORs) controlling for preventive care visits, diabetes, valvular heart disease, smoking, alcohol abuse, obesity, and hypertension. RESULTS: We identified and matched 24 103 cases 18 to 44 years old and 141 811 45 to 65 years old. Those aged 18 to 44 years had increased stroke risk 30 days after ILI (aOR, 1.68 [95% CI, 1.51–1.86]) and reduced risk with any vaccination in the year prior (aOR, 0.92 [95% CI, 0.87–0.99]). Joint effects indicate that ILI was associated with increased stroke risk among those with (aOR, 1.41 [95% CI, 1.08–1.85]) and without (aOR, 1.73 [95% CI, 1.55–1.94]) vaccinations in the prior year ( P interaction =0.16). Among those aged 45 to 65 years, adjusted analyses indicate increased stroke risk for those with ILI (aOR, 1.32 [95% CI, 1.26–1.38]), although there was no effect of vaccinations (aOR, 1.00 [95% CI, 0.97–1.02]). Joint effects indicate that ILI was not associated with stroke among those with any vaccination (aOR, 1.07 [95% CI, 0.96–1.18]) but was associated with increased risk among those without vaccinations ([aOR, 1.39 [95% CI, 1.32–1.47]; P interaction <0.001). CONCLUSIONS: ILI was associated with increased stroke risk in the young and middle-aged, while vaccinations of any type were associated with decreased risk among the young. Joint effects of ILI and vaccinations indicate vaccinations can reduce the effect of ILI on stroke.

Individual and Joint Effects of Influenza-Like Illness and Vaccinations on Stroke in the Young: A Case-Control Study: Can You Catch a Stroke?

“…14 An acute febrile illness was more common within 4 weeks among those who had a stroke (8.7%) than in controls (5.6%; aOR, 1.18 [95% CI, 1.01-1.39]). Consistent with the report by Vollmer et al, 12 influenza vaccination was associated with lower odds of all stroke (aOR, 0.53 [95% CI, 0.46-0.60]), ischemic stroke (aOR, 0.57 [95% CI, 0.50-0.67]), and hemorrhagic stroke (aOR, 0.34 [95% CI, 0.25-0.46]). Addressing the biological gradient Bradford Hill consideration, stroke risk was lower among those with 5 influenza vaccinations compared with those who had 1 to 4 vaccinations over the prior 5 years.…”

“…The report by Vollmer et al 12 adds to this body of data. This case-control study using data from employee-sponsored insurance programs investigated the relationship between ILI, any type of vaccination, and the combined effects of ILI and vaccinations on stroke in young and middle-aged adults.…”

Advances in Stroke: Treatments-Preventive

“…Another case-control study found that having an influenza-like illness was not associated with stroke among those who received any vaccination (the majority likely for influenza; adjusted odds ratio, 1.07 [95% CI, 0.96–1.18]) but was associated with increased risk among the unvaccinated (adjusted odds ratio, 1.39 [95% CI, 1.32–1.47]; P for interaction <0.001). 10 Taken together, these and other studies suggest vaccination may be an effective strategy for reducing stroke risk.…”

Evaluation of Stroke Risk Following COVID-19 mRNA Bivalent Vaccines Among U.S. Adults Aged ≥65 Years

“…al reported higher stroke odds ratio following influenza infection compared to vaccination. 24 The clinical significance of the risk of stroke following vaccination must be carefully considered together with the significant benefits of receiving an influenza vaccination. Because the current framework of our SCCS study does not compare the vaccinated to the unvaccinated populations, it does not account for the reduced rate of severe influenza following vaccination.…”