Workplace Flu Vaccinations: Supporting Heart Health

Most people underestimate the flu

Many people think of the flu as a bad few days in bed, a fever, body aches, and time away from work. Those symptoms are real, but they are not the full story.

Influenza is not the same as a common cold. It is a viral infection that can put intense stress on the body. For some people, that stress can be serious enough to trigger a heart attack or stroke. This is especially important for older adults, people with heart disease, and anyone with other long term health conditions. It also matters for people who think they are otherwise well.

The Heart Foundation of New Zealand notes that even people without a diagnosed heart condition are more likely to have a heart attack after the flu. That makes influenza more than a seasonal illness. It is also a cardiovascular risk factor that deserves more attention. 

Why the flu can affect the heart

When you catch the flu, your immune system responds quickly. That response helps fight the virus, but it also causes inflammation throughout the body.

Inflammation can affect the heart and blood vessels in a few important ways. It can make blood more likely to clot. It can place extra strain on the heart through fever, dehydration, and a faster heart rate. It can also disturb fatty plaque already sitting in the arteries. If that plaque becomes unstable and ruptures, a clot can form and block blood flow to the heart or brain.

That is one reason doctors take influenza seriously in people with cardiovascular risk. Research on inflammation and thrombosis shows that infection can push the body into a state where clotting and vascular events become more likely. 

The risk rises quickly after infection

One of the strongest studies in this area looked at laboratory confirmed influenza and hospital admissions for heart attack. It found that the risk of acute myocardial infarction was about six times higher in the first seven days after confirmed flu infection than during the control period.

That finding supports what clinicians have suspected for years. A respiratory infection can be the event that tips a person from stable heart disease into a medical emergency. Other studies have also shown that acute infections can raise the risk of cardiovascular events for longer than just a few days, especially in people who already have underlying vascular disease. 

This matters because not every person at risk knows they are at risk. Some people have narrowing in their arteries and no obvious symptoms. For them, the flu may be the trigger that reveals a hidden problem.

Prevention matters more than many people realise

If influenza can trigger heart attacks and strokes, then preventing influenza becomes part of protecting the heart.

That is where annual flu vaccination becomes important. A large meta analysis of randomised clinical trials found that influenza vaccination was linked with fewer major cardiovascular events overall. In that analysis, 3.6 percent of vaccinated patients had a major cardiovascular event within 12 months, compared with 5.4 percent in the placebo or control group. The benefit was strongest in people with recent acute coronary syndrome, where risk was reduced by 45 percent. 

The Heart Foundation of New Zealand also advises that flu vaccination lowers the chance of getting seriously unwell and helps reduce the risk of heart events. Health New Zealand recommends a flu vaccine every year, and it is funded for people aged 65 and over, pregnant people, and people with long term conditions including heart conditions. 

A simple step that supports heart health

Flu vaccination should not be seen only as a way to avoid fever and time off work. It can also be viewed as part of wider cardiovascular prevention.

For someone with heart disease, diabetes, chronic lung disease, or older age, the flu vaccine is a practical step that may reduce the chance of both severe infection and a serious heart event. It does not replace blood pressure treatment, cholesterol management, smoking cessation, exercise, or regular medical care. It sits alongside them.

Influenza can do more than make you feel miserable. In some people, it can trigger a heart attack or stroke. Preventing flu is one way to lower that risk, and an annual flu vaccine remains one of the simplest tools we have. Contact us to book in your workplace flu vaccinations, or click here to read more.

Sources

• Heart Foundation New Zealand. (n.d.). Flu vaccinations reduce risk of heart events. Retrieved March 26, 2026.
• Health New Zealand, Te Whatu Ora. (2025, November 19). Flu (influenza) vaccine.
• Immunisation Advisory Centre. (n.d.). Influenza. Retrieved March 26, 2026, from
• Kwong, J. C., Schwartz, K. L., Campitelli, M. A., Chung, H., Crowcroft, N. S., Karnauchow, T., Katz, K., Ko, D. T., McGeer, A. J., McNally, D., Richardson, D. C., Rosella, L. C., Simor, A., Smieja, M., Zahariadis, G., & Gubbay, J. B. (2018). Acute myocardial infarction after laboratory-confirmed influenza infection. The New England Journal of Medicine, 378(4), 345–353.
• Behrouzi, B., Bhatt, D. L., Cannon, C. P., Vardeny, O., Lee, D. S., Solomon, S. D., Udell, J. A., & others. (2022). Association of influenza vaccination with cardiovascular risk: A meta-analysis. JAMA Network Open, 5(4), e228873.
• Stark, K., & Massberg, S. (2021). Interplay between inflammation and thrombosis in cardiovascular pathology. Nature Reviews Cardiology, 18(9), 666–682.