Latest COVID vaccine may have unexpected health benefit, study suggests

The latest COVID-19 vaccine (2024-2025) has been linked to fewer serious heart-related events among U.S. veterans.

New research confirmed a small reduction in COVID-related cardiovascular events, or COVID-19-associated MACE, due to the vaccine.

MACE (major adverse cardiovascular events) is a composite measure of serious heart-related outcomes. It typically includes cardiovascular death, heart attack and stroke, and may also include hospitalization for heart failure.

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Using health records from the U.S. Department of Veterans Affairs, the researchers compared two groups of veterans — one that received the COVID and flu vaccine on the same day (nearly 350,000 people) and another group that received only the flu vaccine (nearly 700,000 people).

Out of more than one million veterans studied, the average age was about 70 and 92% were male, according to a press release.

Within about eight months, the results showed that those who received the 2024-2025 COVID vaccine had a lower risk of COVID-associated major cardiovascular events, with a relative vaccine effectiveness of 37.7%.

The COVID vaccine was linked to a 57.9% lower risk of cardiovascular death, 38.5% lower risk of heart attack and 41.9% lower risk of hospitalization for heart failure, the researchers stated. The result for stroke was not statistically significant.

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The benefit was greatest among adults ages 75 and older and those with underlying health conditions. In people over 75, the vaccine was 50.7% effective at preventing COVID-associated MACE.

As the study was observational, it could not prove cause and effect between the COVID-19 vaccine and lower risk of cardiovascular events, but only highlighted an association.

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Dr. Glenn Hirsch, cardiologist at National Jewish Health in Denver, Colorado, called these results "not overall surprising" in an interview with Fox News Digital.

"This result is consistent with previous studies of the COVID-19 vaccine and other vaccines against infectious diseases [in] preventing cardiovascular events, including heart attack, cardiovascular cause of death or hospitalizations," he said.

Acute inflammation in the body from infections like COVID-19 increases the risk of cardiovascular events and can cause further complications, according to the doctor.

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"This can lead to a higher risk of blood clotting, but can also make arterial plaques susceptible to rupture, which then leads to clot formation to heal a ruptured plaque," he said. "This clotting can cause a near-total or complete occlusion of an artery, leading to these cardiovascular events."

"Vaccines either prevent infection or reduce the severity of infection and subsequent inflammation, lowering the cardiovascular risk."

Despite the positive outcome, the overall benefit of the vaccine in this study was less than in previous studies, according to Hirsch, who was not involved in the research.

This could be due to the lower severity of illness seen in more recent COVID-19 variants, as well as immunity from prior infections among unvaccinated people, he noted. There has also been a decline in COVID testing, making it more difficult to link cardiovascular events to the virus.

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"The bottom line [is] that there is still evidence of benefit from COVID-19 vaccination like many other infectious disease vaccinations, and people should be encouraged to discuss these with their healthcare team annually," Hirsch advised.

"This is an observational trial and there can always be some confounding after necessary statistical adjustments and other potential benefits or harms, including adverse effects from vaccines that were not investigated in this study," he added.