Despite continued advantages, anti-vaccine messaging has reduced vaccination uptake.
While the majority of Americans have skipped seasonal COVID-19 vaccines, the updated formulations continue to offer substantial protection against cardiovascular disease, particularly for individuals over age 75 and those with pre-existing health conditions. That is according to a new study that analyzed data from over 1 million patients within a US Department of Veterans Affairs (VA) health system.
This result expands on earlier evidence showing that the vaccines significantly lower the risk of COVID-19-related cardiovascular issues, especially heart attacks and strokes. However, it was not guaranteed that this benefit would persist over time—as the virus evolved, the vaccines were modified, population-level immunity grew from prior infection and vaccination, and the risk of severe outcomes decreased.
The new study, published in JAMA Internal Medicine, found that the 2024–2025 COVID-19 vaccine continued to guard against COVID-19-associated "major adverse cardiovascular events" (MACE), which encompass cardiovascular death, heart attack, stroke, and hospitalization due to heart failure.
The study incorporated electronic medical record data from 1,039,659 patients in the VA's St. Louis Health Care System. All patients received a seasonal flu shot between September 3, 2024, and December 31, 2024, with some also receiving a COVID-19 vaccine concurrently. Of the 1,039,659 patients, 349,085 received both shots, while 690,574 received only the flu shot. The latter group served as the control group for the study.
After eight months of follow-up, the researchers looked for documented COVID-19 cases and compared MACE events between the two groups. Overall, the COVID shots' vaccine effectiveness against MACE events was 38 percent. In absolute numbers, the benefit is modest. The study estimated that the shots reduced the rate of COVID-19-associated MACE events from about 5 per 10,000 to 3 per 10,000. Examining subgroups, the benefits were most pronounced among those aged 75 and older and those with underlying health conditions.
Overlooked advantages
The researchers, led by epidemiologist Ziyad Al-Aly at the St. Louis VA, also examined MACE and deaths without documented COVID-19 cases. Here, the benefits of COVID-19 vaccines were more pronounced, suggesting that COVID-19 cases may have been missed or undiagnosed. The shots appeared to lower the rate of MACE from 382 per 10,000 to 358, and the rate of death from 223 to 207.
"Extrapolating these estimates to a population of 1 million people, vaccination could plausibly be associated with averting approximately 2,370 MACE events and 1,580 deaths over an 8-month period," the researchers note, though they advise caution in interpreting the finding.
The study has limitations, including that most of the US veteran population is older, White, and male, making it likely that the findings cannot be generalized to the broader population. Still, the results indicate that the vaccines continue to provide cardiovascular protection against COVID-19, which should factor into individuals' decisions on whether to get an annual COVID-19 booster. An accompanying study also published in JAMA Internal Medicine on Monday found that the vaccines still directly protect against COVID-19, reducing the risk of hospitalization and critical illness by 35 percent and 41 percent, respectively.
In an accompanying editorial, Robert Califf, a cardiologist and former Food and Drug Administration commissioner, wrote that the data from the two studies "provide strong evidence of a favorable balance of benefit to risk for updated COVID-19 vaccine boosters across the population." However, he lamented that despite that strong evidence, national views are being influenced by the "general antivaccination statements from the US Department of Health and Human Services," which is led by anti-vaccine Health Secretary Robert F. Kennedy Jr.
Only 17.5 percent of adults and 22.6 percent of people over age 65 in the US have received the 2025–2026 COVID shot, according to federal data.
"The politicization of COVID-19 vaccination and messenger RNA vaccines in general has taken a toll on the longevity and functional status of those in the US," Califf wrote. He called for researchers to collect more data on the vaccine's benefits and engage with the public about the findings, particularly on social media, to counter anti-vaccine messaging.