The following are key points to remember from this article about the influenza vaccine and investing in cardiovascular (CV) health:

1. The authors reviewed the risk/benefit of influenza vaccination, which is underutilized throughout the world. They concluded that all CV health care providers should promote influenza vaccination utilization and other prevention measures with defined implementation strategies, and by combating misinformation and promoting trust and safety.
2. Influenza infection is caused by a family of viruses transmitted through respiratory droplets and contributes to nearly a million hospitalizations and over 30,000 deaths annually in the United States. Annual influenza vaccine has been promoted widely with an emphasis on the elderly and those at high risk for comorbidities. The present recommendation includes everyone 6 months of age and older. The link between viral respiratory infection and nonpulmonary organ-specific injury, including cardiac injury and acute coronary events, has become increasingly appreciated during the current coronavirus disease 2019 (COVID-19) pandemic.
3. Amongst the pathogenesis beyond the direct effect of the virus(s) includes the intense inflammatory cytokine response during the acute phase, which has been linked to accelerating atherogenesis and direct myocardial depression. There is evidence that influenza vaccination reduces CV events including death in persons with atherosclerotic CV disease (CVD) with greater benefit in those with recent acute coronary syndromes and in persons with chronic heart failure (CHF), there is a reduction in all-cause and CV mortality, and hospitalizations.
4. Because of the reduced vaccine immune response with aging and CVD, the Food and Drug Administration approved high-dose influenza vaccine for the elderly for 2021-2022. High dose was shown to reduce polymerase chain reaction (PCR)-confirmed influenza compared to standard dosing. A clinical trial was needed to determine the relative value of high versus standard vaccine dosing to reduce risk in persons with CVD.
5. The INVESTED trial (INfluenza Vaccine to Effectively Stop CardioThoracic Events and Decompensated heart failure) was designed to compare two doses of vaccine in 5,260 high-risk CVD patients to determine if high dose reduced the risk of composite death from any cause or cardiopulmonary hospitalizations (Vardy O, et al., JAMA 2021;325:39-49). The study, conducted over 3 years, had about one-third qualify by myocardial infarction and two-thirds by CHF, 35% were less than 65 years, and 50% were women. High-dose vaccine did not reduce primary or secondary endpoints or prespecified subgroups. The low total frequency of endpoints in both groups and relatively low number of influenza-associated hospitalizations suggested the low attributable risk of influenza could explain the lack of difference in primary endpoints. The vaccine effectiveness ranged from 29-40%, which also could have influenced the results. The higher dose of vaccine would not be expected to influence protection if the match between viral antigens in the vaccine and seasonal influenza strains was poor, as has been the case.
6. The authors concluded the INVESTED trial results should not dampen the enthusiasm for the vaccination, nor does it counteract prior evidence showing high-dose vaccine reduced influenza illness. In fact, data suggest vaccination may provide similar CVD prevention to smoking cessation and at a very low cost and exceedingly low rate of serious adverse events.
7. Despite the evidence in favor, routine yearly vaccination is poor, even in high-risk cohorts such as CHF in whom the rate was only 53% in North America. Similarly, amongst the INVESTED high-risk participants, only 59% were vaccinated in the year prior to the randomization, and in those <65 years, it was much lower.
8. Hopefully the lessons learned from the COVID-19 vaccine and use of simple measures to reduce droplet exposure including hand washing, physical distancing, and masking will influence both health care practitioners and their patients, employers, and the general public to embrace the same common sense practiced procedures and vaccine to prevent the flu.

Clinical Topics: Acute Coronary Syndromes, COVID-19 Hub, Heart Failure and Cardiomyopathies, Prevention, Acute Heart Failure

Keywords: Acute Coronary Syndrome, Antigens, Viral, Atherosclerosis, Coronavirus, COVID-19, Cytokines, Heart Failure, Immunity, Influenza Vaccines, Influenza, Human, Myocardial Infarction, Polymerase Chain Reaction, Primary Prevention, Smoking Cessation, Vaccination

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