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Prevention of Acute Cardiovascular Events by Flu Vaccine
Quick Takes
- Individuals with both high and low cardiovascular risk had a reduced incidence of a first acute cardiovascular event after influenza vaccination.
- The reduced incidence was largest in the 15–28 days after vaccination but persisted to 120 days.
- Improving uptake remains a public health priority, both to protect individuals from influenza and complications such as acute cardiovascular events.
Study Questions:
What is the association between influenza vaccination and acute cardiovascular events, considering individual cardiovascular risk?
Methods:
The investigators used linked Clinical Practice Research Datalink, Hospital Episode Statistics Admitted Patient Care, and Office for National Statistics mortality data from England between September 1, 2008, and August 31, 2019. From the data, individuals aged 40–84 years with a first acute cardiovascular event and influenza vaccination occurring within 12 months of each September were selected. Using a self-controlled case series analysis, season-adjusted cardiovascular risk stratified incidence ratios (IRs) for cardiovascular events after vaccination compared with baseline time before and >120 days after vaccination were generated. The authors calculated IRs using conditional Poisson regression for acute cardiovascular events occurring within each risk period stratum compared with baseline and further adjusted for season using the binary classification of warm months (April–September) and cool months (October–March).
Results:
A total of 193,900 individuals with a first acute cardiovascular event and influenza vaccine were included. 105,539 had hypertension and 172,050 had a QRISK2 score ≥10%. In the main analysis, acute cardiovascular event risk was reduced in the 15–28 days after vaccination (IR, 0.72; 95% confidence interval [CI], 0.70–0.74) and, while the effect size tapered, remained reduced to 91–120 days after vaccination (IR, 0.83; 95% CI, 0.81–0.88). Reduced cardiovascular events were seen after vaccination among individuals of all age groups and with raised and low cardiovascular risk.
Conclusions:
The authors concluded that the influenza vaccine may offer cardiovascular benefit among individuals at varying cardiovascular risk.
Perspective:
This study reports that individuals with both high and low cardiovascular risk had a reduced incidence of a first acute cardiovascular event following influenza vaccination after adjusting for season. Furthermore, the reduced incidence was largest in the 15–28 days after vaccination but persisted to 120 days. Of note, the protective effect was evident across all age groups in the main analyses but was confined to those aged ≥65 years in the final sensitivity analysis with follow-up from vaccination date. While additional studies are indicated to better characterize those who would derive the most cardiovascular benefit from influenza vaccine, improving uptake remains a public health priority at this time, both to protect individuals from influenza and complications such as acute cardiovascular events.
Clinical Topics: Acute Coronary Syndromes, Geriatric Cardiology, Prevention, Hypertension
Keywords: Acute Coronary Syndrome, Cardiovascular Diseases, Geriatrics, Hypertension, Influenza Vaccines, Influenza, Human, Myocardial Infarction, Primary Prevention, Risk Assessment, Risk Factors, Seasons, Vaccination
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