Updated COVID vaccines cut risk of hospital care, heart complications, new data reveal

The vaccine was most effective during the first two months after vaccination and waned over time. Protection against ED/UC visits, for example, declined from 38% seven to 59 days after vaccination to 11% after 180 to 299 days.

Among immunocompromised adults, vaccine effectiveness (VE) against hospitalization was 24% and also waned over time, dipping to no protection 180 to 299 days after vaccination. 

“Results of this study demonstrate that COVID-19 vaccines continued to provide benefit to people at the highest risk of severe COVID-19 outcomes,” write the authors, concluding that “receipt of 2024-2025 COVID-19 vaccination was associated with additional protection against medically attended COVID-19 beyond an individual’s existing immunity; however, protection appeared to wane over time.”

Reduced cardiovascular risk in older adults

A second study, led by researchers at the US Department of Veterans Affairs, examined whether the 2024-25 vaccine was tied to a lower risk of COVID-19–associated major adverse cardiovascular events (MACE), which include cardiovascular death, heart attack, stroke, and hospitalization for heart failure.

Using health records from more than 1 million veterans who received the flu vaccine from September to December 2024, the researchers compared people who received a COVID vaccine at the same time as a flu vaccine with those who received only the flu vaccine.

After eight months, receipt of the COVID vaccine was associated with a 37.7% reduction in MACE, but VE was statistically significant only in adults older than 75 years, who experienced a 50.7% reduction in MACE as well as the largest absolute risk reduction. 

While the researchers observed statistically significant VE in both those with and without comorbid conditions, the absolute benefit was “consistently and substantially greater” for those who had other chronic conditions.

“While the reduction in COVID-19–associated MACE 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,” write the researchers. 

Benefits outweigh risks

Despite all Americans having been either infected with and/or vaccinated against COVID at this point, writes Califf in the commentary, the studies’ findings demonstrate that “updated booster vaccines provide continued protection against major adverse clinical outcomes, including lower risks of major cardiovascular events, hospitalizations, and all-cause death.”

And even though the magnitude of the protection is modest and wanes over time, argues Califf, the cardiovascular benefits of vaccination outweigh the potential risks. What’s more, he adds, studies continue to suggest major risks tied to COVID infection, including neurodevelopmental disorders in children born to those with serious COVID infections. 

Post-COVID condition, also known as long COVID, is another important consideration. “Ongoing studies point out the substantial effects of post–COVID-19 condition. Millions of individuals in the US, including a substantial number of children, experience loss of function and diminished quality of life due to the disease’s sequelae,” Califf writes. “Many observational studies have found an association between previous vaccination and a reduced risk of post–COVID-19 condition.” 

Overall, the commentary argues, accumulating evidence supports COVID vaccination. “The studies reported herein, combined with previous data, provide strong evidence of a favorable balance of benefit to risk for updated COVID-19 vaccine boosters across the population,” he writes.