Updated COVID shots linked to lower heart risk in VA study

Updated COVID-19 vaccines were associated with lower rates of serious heart and vascular problems in a study of more than 1 million patients in the Veterans Affairs health system. The finding matters because researchers say cardiovascular complications remain part of the risk from COVID-19, even as vaccination rates have fallen.

The study, published in JAMA Internal Medicine, examined the 2024-2025 COVID-19 vaccine and its association with what researchers called major adverse cardiovascular events. Those events included cardiovascular death, heart attack, stroke and hospitalization for heart failure.

Epidemiologist Ziyad Al-Aly of the St. Louis VA and colleagues used electronic health record data from 1,039,659 patients in the VA St. Louis Health Care System. All patients in the analysis received a seasonal flu vaccine between Sept. 3 and Dec. 31, 2024.

Within that group, 349,085 patients received a COVID-19 vaccine at the same visit, while 690,574 received only the flu shot. The researchers treated the flu-only group as the comparison group and followed patients for eight months.

After that follow-up period, the researchers reviewed documented COVID-19 infections and compared cardiovascular outcomes between the two groups. They estimated that the COVID vaccine was 38% effective against COVID-associated major adverse cardiovascular events.

In absolute terms, the researchers reported a small change in documented COVID-associated cardiovascular events. The estimated rate fell from about 5 events per 10,000 people to about 3 per 10,000 people among those who received the COVID shot.

The study found the strongest apparent benefit among patients 75 and older and among patients with underlying medical conditions. The authors said those groups had greater protection in subgroup analyses.

Researchers also examined broader outcomes

Al-Aly and colleagues also looked at major cardiovascular events and deaths without requiring a documented COVID-19 diagnosis. They said the stronger associations in that analysis may indicate that some COVID cases were not recorded or diagnosed.

In that broader analysis, the researchers estimated that vaccination was associated with a reduction in major adverse cardiovascular events from 382 per 10,000 people to 358 per 10,000. They also estimated that deaths fell from 223 per 10,000 to 207 per 10,000.

The authors wrote that, if applied to a population of 1 million people, those estimates could correspond to about 2,370 fewer major cardiovascular events and 1,580 fewer deaths over eight months. They cautioned that those figures should be interpreted carefully.

The study has limits. The authors noted that the U.S. veteran population is disproportionately older, White and male, which may limit how well the findings apply to the broader public.

A separate JAMA Internal Medicine study published alongside it found that updated COVID vaccines still reduced the risk of COVID-19 hospitalization by 35% and critical illness by 41%.

In an accompanying editorial, Robert Califf, a cardiologist and former Food and Drug Administration commissioner, wrote that the two studies provide strong evidence that updated boosters have a favorable benefit-risk balance across the population. Califf also criticized what he described as general antivaccination statements from the U.S. Department of Health and Human Services, led by Health Secretary Robert F. Kennedy Jr.

Federal data show low uptake of the current shots. The Centers for Disease Control and Prevention reported that 17.5% of U.S. adults and 22.6% of people 65 and older had received the 2025-2026 COVID vaccine.

Califf wrote that politicization of COVID vaccination and messenger RNA vaccines has harmed longevity and functional status in the United States. He urged researchers to gather more evidence on vaccine benefits and communicate the findings to the public, including on social media.

This story draws on original reporting from Ars Technica.