Influenza & Post-COVID "3-4 Times Higher Risk of Myocardial Infarction": The Connection Between Inflammation, Blood Clots, Infection, and the Heart

Winter is Not Just a "Common Cold" —— The Definitive Link Between Viral Infections and Cardiovascular Events

This winter, it might be wise to reconsider viewing the flu and COVID-19 as merely "an extension of a sore throat."The risk of myocardial infarction and stroke significantly increases in the weeks to months following an infection, as demonstrated by a large-scale systematic review/meta-analysis published in the American Heart Association's (AHA) open-access journal, Journal of the American Heart Association (JAHA). The New York Times (NYT) Well section also detailed these findings.AHA Journals

What Increases and By How Much: Specific Numbers

• Influenza: Within one month post-infection, myocardial infarction is about 4 times, and stroke is about 5 times more likely.American Heart Association

• COVID-19 (SARS-CoV-2): Within 14 weeks post-infection, both myocardial infarction and stroke are about 3 times more likely, with some indications that the increased risk may persist for about a year.American Heart Association

Furthermore, chronic viral infections (those that remain latent or persistent in the body) are also associated with long-term cardiovascular risk increases.

• HIV: Myocardial infarction **+60%, stroke +45%**.

• Hepatitis C (HCV): Myocardial infarction **+27%, stroke +23%**.

• Shingles (Reactivation of VZV): Myocardial infarction **+12%, stroke +18%**.American Heart Association

These figures are based on a meta-analysis pooling 155 studies from screening over 52,000 papers. The scale and methodology provide higher external validity compared to single studies.American Heart Association

Why It Affects the Heart and Blood Vessels: The Leading Mechanism

According to AHA's explanation and related reports, persistent inflammation and a tendency for blood clotting are the main hypotheses. Cytokine responses and increased coagulation that rise during the acute phase continue for a while, leading to plaque destabilization and thrombus formation. As a result, underlying atherosclerosis becomes more likely to "ignite."American Heart Association

(Supplementary) Recently, the hypothesis that infection awakens dormant microbiota within plaques, leading to rupture has also gained attention, but this is still in the verification stage and not yet ready for immediate clinical application.SciTechDaily

Can Vaccines Also Serve as "Preventive Medicine for the Heart"?

This review suggests that infection prevention through vaccines may also contribute to the secondary prevention of cardiovascular events. In fact, there are citations of past reviews indicating that major cardiovascular events were reduced by 34% in the influenza vaccine group. Additionally, large-scale studies have reported that COVID-19 vaccines significantly reduce the risk of heart failure and thrombosis. Analyses suggesting the cardiovascular protective effects of the shingles vaccine are also emerging.Technology Networks

Interpreting "Relative Risk" and "Absolute Risk"

On social media, figures like "3 times" and "5 times" relative risk can easily circulate independently. What’s important is the original probability of occurrence (absolute risk). The absolute risk increase for young people without underlying conditions remains small, but for the elderly, those with medical history, and those with risk factors, the impact of the relative risk increase becomes significant due to a higher "baseline." Behavioral choices considering this "denominator" difference are essential. (This point is a general principle of epidemiological literacy)

Implementation-Based Behavioral Proposals (Assuming a Japanese Winter)

• Vaccination Plan: Advance the timing of vaccinations for influenza/COVID-19 (and shingles for eligible individuals). Those with chronic conditions should optimize individually with their primary care physician.The Guardian

• Balanced Infection Control: In crowded indoor spaces, ventilation, masks, and hand hygiene should be "on." If there are high-risk individuals in the family, consider practical measures such as avoiding sharing rooms during fever periods.

• Self-Monitoring After Infection: For a few weeks, be sensitive to warning signs such as chest pain, shortness of breath, palpitations, hemiplegia, and slurred speech. Do not hesitate to seek emergency care in case of abnormalities.

• Correcting the Baseline: Managing blood pressure, glucose metabolism, lipids, smoking, and sleep to "prepare a less flammable ground" can minimize the damage from relative risk increases.
  
  
  

SNS Reactions (Excerpts)

Immediately after the NYT article was published, the medical and public health communities and patient communities reacted swiftly.

• **Dr. Peter Hotez (Vaccine Researcher)** shared the article link, raising awareness from a public health perspective and contributing to the visibility of the expert community.X (formerly Twitter)

• Long COVID Stakeholders and Support Accounts welcomed it as "belated recognition by mainstream media" and prominently posted calls for continued vigilance regarding long-term effects.X (formerly Twitter)

• Medical and Science Journalists and general users also made calm remarks such as **"not letting relative risk numbers run away on their own."**X (formerly Twitter)

• NYT's Official Facebook Post also spread widely, with discussions in the comments about "how to convey this to family members with medical history" and "the priority of vaccines," leading to practical discussions.facebook.com

Overall, it appears that the perspective of **"infection prevention as part of preventing cardiovascular events"** is gradually being shared by both clinical settings and patients.

Points of Misunderstanding

1. Can Everything Be Prevented by Vaccines Alone?
   No. Vaccines are a powerful tool to reduce the probability of infection, severe illness, and complications, but they are not a complete barrier. Lifestyle habits, ventilation, masks, and multi-layered defenses are needed.The Guardian

2. Does It Not Matter Because You're Young?
   The absolute risk for young people is low but not zero. It is safer to make decisions that avoid overexertion in the weeks following infection, including the timing of returning to sports or resuming business trips. (General principle)

3. Is Only COVID-19 Dangerous?
   This review also showed a strong correlation with influenza. "Seasonal" does not mean safe.American Heart Association
   
   

Summary: This Winter, Focus on "Infection Control for the Heart"

The season of infectious diseases is not just about getting through fever and cough.The increase in cardiovascular events post-infection is being supported by layers of reliable evidence.With a "disaster prevention set to protect the heart" consisting of vaccines, multi-layered defenses, and self-monitoring post-infection, let's calmly overcome the mountain of risks.AHA Journals

Sources (Main)

• AHA News Release (2025/10/29) / Highlights of the JAHA Published Paper.American Heart Association

• Original