American Heart Association Basic Cardiovascular Sciences Meeting. July 27, 2020. Presentation 398.

It may be a while before a vaccine for COVID-19 is available, but recent data presented on 27 July at the virtual American Heart Association (AHA) Basic Cardiovascular Sciences 2020 Scientific Sessions showed a significant benefit of vaccination for another kind of virus.

According to the large retrospective cohort study carried out in the US, patients who received a flu jab have a significantly lower risk for cardiovascular events, including myocardial infarction (MI), transient ischaemic attack (TIA) and all-cause mortality. However, this study also showed that the rate of seasonal flu vaccination among high-risk groups, including people over 50 years old, with chronic medical conditions, obesity and HIV infection, was very low.

Results showed that of the more than 7 million high-risk patients in the database, just over 168,000 received a flu vaccination. Patients over the age of 50 had a vaccination rate of 1.8% compared with 15.3% in the general population despite impressive benefits of vaccination: a 28% lower risk of MI, a 47% lower risk of TIA, and a 73% lower risk of all-cause mortality in the following year. Similar results were recorded among other high-risk groups. The vaccination rate for nursing home residents was 1.8% compared with 9.5% for those living independently. Flu vaccination in nursing home residents was associated with a 14% reduction in MI and a 56% reduction in TIA. Among patients with obesity, 2.4% were vaccinated compared with 9% of those with a healthy weight. And flu vaccination in obese patients was associated with a 41% reduction in MI, a 55% reduction in TIA, and a 76% reduction in all-cause mortality.

These are extraordinary results, yet it looks that at least in the USA, the very people who stand to gain most from flu vaccination are the least likely to get it. The explanation may be a perceived lack of benefit, insufficient promotion and economic barriers to access healthcare in the US settings. There is also the possibility of confounding as the survey looked purely on vaccinations in hospital, and some patients may have received flu jab in primary care.

What is the mechanism behind the reduced risk of cardiac complications in flu vaccination? A potential answer may be inflammation triggered by a viral infection and lung injury with reduced blood oxygen levels which puts more strain on the heart. The virus can also directly damage heart muscle cells and lead to heart failure.

Flu vaccination is even more critical in the context of the COVID-19 pandemic. Just like with flu, the elderly and individuals with comorbidities infected with COVID-19 are at higher risk for adverse cardiac outcomes. It is hoped that the high profile of COVID-19 will lead to better uptake of vaccination when a safe and efficient vaccine is developed. Until then, we should protect ourselves with what we have - including flu jab.

Just as a reminder, a flu vaccine is offered free of charge on the NHS to people at risk, including patients over 65, pregnant women, patients with certain medical conditions, care home residents, and frontline health and social care workers.