JAMA Internal Medicine published the cohort study on 15 June. The paper's key points said it included 1,039,659 participants from US Department of Veterans Affairs electronic health records. Researchers compared veterans who received same-day 2024-25 Covid and influenza vaccines with veterans who received the 2024-25 influenza vaccine alone.
That design matters. This was not a randomised trial in which people were assigned to vaccination or no vaccination. It was an observational study using health-record data to emulate a target trial. The study can estimate an association after adjustment, but residual confounding remains possible: people who accept two vaccines on the same day may differ from people who accept only influenza vaccination in ways the data cannot fully capture.
The primary finding, according to JAMA's summary and the EurekAlert release for the paper, was that receipt of the 2024-25 Covid vaccine was associated with lower risk of Covid-associated major adverse cardiovascular events. The reduction was more prominent among veterans aged 75 or older and among those with comorbidities.
That is clinically plausible. Covid infection can raise short-term cardiovascular risk, especially in older people and those with existing illness. A vaccine that reduces infection severity or infection-related complications could therefore reduce some downstream cardiac events. STAT reported that the study tied vaccination to a nearly 24% reduction in all-cause cardiac events and that the authors estimated the association could translate into about 3,500 major cardiac events and 2,400 deaths prevented annually per 1mn people.
The stronger claim is also the one that needs the most care. JAMA's summary said the reduction in Covid-associated major adverse cardiovascular events was modest, while the larger reduction in all-cause events suggested protection against an undetected burden of SARS-CoV-2 and its sequelae. That interpretation is reasonable as a hypothesis from the data. It is not the same as proving every avoided all-cause cardiac event was caused by avoided Covid infection.