Older adults who received the latest COVID-19 vaccine were significantly less likely to suffer serious heart-related complications, according to a major new study involving more than 1 million U.S. veterans.
The research, published in JAMA Internal Medicine, found that people who received the 2024–2025 COVID-19 vaccine had a lower risk of major adverse cardiovascular events—including heart attacks, strokes, heart failure hospitalizations and cardiovascular deaths—during the following eight months.
Researchers analyzed health records from more than 1 million veterans who received flu shots between September and December 2024.
Roughly one-third of the veterans also received a COVID-19 vaccine on the same day, allowing scientists to compare outcomes between vaccinated and unvaccinated groups.
The results were striking.
Stock image: Row of Coronavirus vaccine flasks.
The researchers found a nearly 38% reduction in COVID-related cardiac events among the veterans—most notably among patients who were 75 or older, or who had other chronic conditions.
Interestingly, the study showed that the vaccine had a secondary effect: It decreased all-cause cardiac events by 24%.
“While the reduction in COVID-19–associated [major adverse cardiovascular events] was modest, the substantially larger reduction in all-cause MACE suggests that the vaccine’s protective association extends to the hidden burden of undetected SARS-CoV-2 and its sequelae,” the researchers wrote in the study.
Lasting Effects
COVID-19 affects the body in a wide variety of ways, and the virus is still strong in 2026, long after many Americans have relaxed their precautionary actions.
A new, heavily mutated version of the virus was detected in 25 states as recently as March.
Long COVID has been shown to leave lasting effects that hang on far beyond the usual effects of a virus, sometimes ranging from a few months to several years.
The Centers for Disease Control and Prevention (CDC) says that fatigue, difficulty breathing and even trouble with memory and thinking (a symptom often known as brain fog) are hallmarks of long COVID, which can result in disability in some individuals.
The Effects of Inflammation
Damage to the heart is another concerning and well-documented side effect of COVID.
To fight off COVID, the body often experiences inflammation as the immune system is activated to battle the disease, but for some people, the immune system is overly active.
Excessive inflammation can hurt the heart in a variety of ways, causing the heart to lose its regular rhythm, creating blood clots and even causing life-threatening heart failure.
The COVID vaccine protected many adults against these effects, according to the researchers.
In an interview with STAT News, Ziyad Al-Aly—one of the study’s authors—noted that one explanation is that people who had undiagnosed COVID-19 may have simply chalked up their symptoms to being “under the weather” before experiencing a COVID-related cardiac event a few weeks later.
In either case, the researchers pointed out that the protections of a COVID vaccine can do more than just minimize symptoms.
“These findings provide timely evidence to help inform clinical and public health discussions about the role of updated COVID-19 vaccines in the current epidemiologic context,” the researchers wrote.
Newsweek has reached out to the study authors for comment via email.
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