Influenza places a significant health burden on the US population, resulting in an estimated 140,000-810,000 hospitalizations and 12,000-61,000 deaths annually.¹ Influenza is associated with acute cardiovascular events, including heart failure exacerbations,² ischemic episodes,² and overall cardiovascular mortality, even in people with no prior cardiac history.³ In individuals with cardiovascular risk factors who become infected with influenza, there is a significant association between influenza and acute myocardial infarction.⁴

In the context of the coronavirus disease 2019 (COVID-19) pandemic, it has never been more important to receive an influenza vaccine, especially for those living with high-risk medical conditions, including cardiovascular disease. Although the Southern hemisphere experienced a substantial reduction in influenza virus transmission during its 2020 influenza season following widespread adoption of community mitigation measures to reduce the spread of COVID-19,⁵ there is no guarantee the United States will have a similar experience due to the phased reentry into schools and the reopening of businesses, the loosening of government-issued COVID-19 physical distancing measures,⁶ and varying compliance with mask wearing.⁷ This year, co-circulation of SARS-CoV-2, the virus that causes COVID-19, and influenza viruses is likely. Persons with heart disease are at higher risk for developing serious complications from influenza,⁸ and many of those with serious heart conditions are also at increased risk of severe illness from SARS-CoV-2.⁹ While there is not yet a licensed COVID-19 vaccine available, there is a safe, effective influenza vaccine that has been administered for more than 50 years.¹⁰

Influenza vaccination is the best way to prevent influenza and has been shown to reduce the risk of influenza-related complications,^11,12 preventing an estimated 5.4 million symptomatic influenza illnesses, 71,000 hospitalizations, and 5,450 deaths annually over the last decade.¹³ Influenza vaccination is also an effective strategy for the prevention of cardiovascular-related morbidity and mortality associated with influenza. A recent study highlighted the importance of influenza vaccination in patients hospitalized with laboratory-confirmed influenza: patients who had been vaccinated against influenza at least 2 weeks before hospitalization had lower risks of acute heart failure and acute ischemic events compared with unvaccinated peers.² Despite evidence that influenza vaccination has been associated with an 18% reduction in both all-cause mortality and cardiovascular death,¹⁴ it is widely underutilized among adults in general and among individuals with cardiovascular disease (¹⁵, and unpublished data, CDC). Among individuals with atherosclerotic cardiovascular disease, only 37% of those aged 18-49 years and 55% of those aged 50-64 years received an influenza vaccination in 2019-2020 (unpublished data, CDC). Influenza vaccination does not require behavior change or a daily intervention, yet it prevents cardiovascular events with comparable effectiveness as other evidence-based approaches that do, including statin therapy, antihypertensive therapy, and smoking cessation.¹⁶

Complications from influenza,¹⁷ COVID-19,¹⁸ and heart disease also disproportionately affect racial and ethnic minority populations.¹⁹ Sociodemographic disparities in influenza vaccination exist;²⁰ 52.8% of non-Hispanic White adults received influenza vaccination in the 2019-2020 season compared with 41.2% of non-Hispanic Black adults.¹⁵ Lower influenza vaccination rates have been consistently found among persons lacking a usual source of care or insurance, persons with lower education or income, and persons who are non-Hispanic Black or Hispanic relative to comparison groups.^21,22

This year, there may be additional barriers to influenza vaccination. These include less opportunity for worksite vaccination clinics, concerns over leaving home for vaccination and risking SARS-CoV-2 exposure, and loss of employment impacting the ability to afford vaccination. Likewise, in-person clinic visits, and visits with primary care clinicians may be cancelled or shifted to telehealth encounters making vaccination logistically more challenging. Additionally, some individuals may be less inclined to receive an influenza vaccination this year because they perceive themselves to be at less risk of influenza infection due to avoiding crowds, mask wearing, and practicing physical distancing measures.

In 2006, the American Heart Association and American College of Cardiology published a consensus statement on secondary prevention for patients with coronary or other atherosclerotic vascular disease that recognized influenza vaccination as a Class 1B recommendation.²³ Additionally, the Centers for Disease Control and Prevention and the Advisory Committee on Immunization Practices have recommended influenza vaccination for everyone 6 months and older, including those with high-risk conditions, such as heart disease, for decades.²⁴ In light of data demonstrating the benefits of an annual influenza vaccination for individuals with cardiovascular disease,^11,12 it is critical that all members of the cardiovascular care team incorporate the Standards for Adult Immunization Practice at each patient encounter, which include assessing vaccination status at every visit, giving strong vaccine recommendations (Image 1), either offering vaccination to patients or referring them to a place that provides vaccines, such as the nearest pharmacy, and documenting vaccines administered in their jurisdiction's immunization information system.²⁵

Image 1

To support increased influenza vaccination coverage this year, influenza vaccination should be discussed at each visit with a healthcare professional. For some patients, an encounter with their cardiologist might be their only visit with a clinician during influenza season, making this a valuable opportunity to offer vaccination. For patients who have annual visits with their primary care provider, their visit may not occur during influenza season, thus highlighting the importance of assessing influenza vaccination status by cardiologists and other specialists. Vaccination messages should be established as an integral part of each visit, and protocols, such as reminder recall systems and standing orders, should be implemented to best promote vaccination.²⁶

Influenza vaccination is a proven strategy to reduce influenza and its associated complications, as well as prevent influenza-associated cardiovascular events. If this annual intervention is widely implemented, it will help reduce the healthcare burden associated with influenza complications. It is the responsibility of the entire cardiovascular care team to ensure their patient population receives an annual influenza vaccination. This year, in the context of the COVID-19 pandemic, having patients vaccinated against influenza is especially important. Each patient encounter during the influenza season provides an opportunity to help patients understand the importance of influenza vaccination for themselves, their families, and their community. Annual influenza vaccination is one of many important strategies at the heart of cardiovascular disease prevention. Each member of the cardiovascular care team can contribute to increasing influenza vaccination coverage in this population, thereby preventing influenza-related hospitalizations and death.

References

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2. Chow EJ, Rolfes MA, O'Halloran A, et al. Acute cardiovascular events associated with influenza in hospitalized adults: a cross-sectional study. Ann Intern Med 2020;173:605-13.
3. Nguyen JL, Yang W, Ito K, Matte TD, Shaman J, Kinney PL. Seasonal influenza infections and cardiovascular disease mortality. JAMA Cardiol 2016;1:274-81.
4. Kwong JC, Schwartz KL, Campitelli MA, et al. Acute myocardial infarction after laboratory-confirmed influenza infection. N Engl J Med 2018;378:345-53.
5. Olsen SJ, Azziz-Baumgartner E, Budd AP, et al. Decreased influenza activity during the COVID-19 pandemic - United States, Australia, Chile, and South Africa, 2020. MMWR Morb Mortal Wkly Rep 2020;69:1305-9.
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12.  Thompson MG, Pierse N, Sue Huang Q, et al. Influenza vaccine effectiveness in preventing influenza-associated intensive care admissions and attenuating severe disease among adults in New Zealand 2012-2015. Vaccine 2018;36:5916-25.
13. Estimated Number of Influenza Illnesses, Medical Visits, Hospitalizations, and Deaths Averted by Vaccination, by Age Group, 2010-11 through 2019-20 Influenza Seasons (CDC website). 2020. Available at https://www.cdc.gov/flu/vaccines-work/past-burden-averted-est.html. Accessed 10/20/2020.
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17. Flu Disparities Among Racial and Ethnic Minority Groups (CDC website). 2020. Available at https://www.cdc.gov/flu/highrisk/disparities-racial-ethnic-minority-groups.html. Accessed 10/14/2020.
18. Wilder JM. The disproportionate impact of COVID-19 on racial and ethnic minorities in the United States. Clin Infect Dis 2020;Jul 10:[Epub ahead of print].
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20. Quinn SC, Jamison A, An J, Freimuth VS, Hancock GR, Musa D. Breaking down the monolith: understanding flu vaccine uptake among African Americans. SSM Popul Health 2018;4:25–36. 
21. Grandhi GR, Mszar R, Vahidy F, et al. Sociodemographic disparities in influenza vaccination among adults with atherosclerotic cardiovascular disease in the United States. JAMA Cardiol 2020;Sep 9:[Epub ahead of print].
22. Sperling LS, Albert MA, Koppaka R. Disparities in influenza vaccination-opportunity to extend cardiovascular prevention to millions of hearts. JAMA Cardiol 2020;Sep 9:[Epub ahead of print].
23. Smith SC Jr, Allen J, Blair SN, et al. AHA/ACC guidelines for secondary prevention for patients with coronary and other atherosclerotic vascular disease: 2006 update: endorsed by the National Heart, Lung, and Blood Institute. Circulation 2006;113:2363-72.
24. Grohskopf LA, Alyanak E, Broder KR, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices - United States, 2020-21 influenza season. MMWR Recomm Rep 2020;69:1-24.
25. National Vaccine Advisory Committee. Recommendations from the National Vaccine Advisory committee: standards for adult immunization practice. Public Health Rep 2014;129:115-23.
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Clinical Topics: COVID-19 Hub, Dyslipidemia, Prevention, Nonstatins, Novel Agents, Statins

Keywords: Primary Prevention, Secondary Prevention, COVID-19, Influenza Vaccines, Influenza, Human, American Heart Association, Cardiovascular Diseases, Antihypertensive Agents, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Coronavirus, severe acute respiratory syndrome coronavirus 2, Ethnic Groups, Seasons

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