2024–2025 COVID Vaccine Linked to Lower Risks of Hospitalization and Death Among U.S. Veterans

It was found that U.S. veterans receiving the 2024–2025 COVID-19 vaccine were linked to lower risks of emergency department visits, hospitalizations and deaths over six months of follow-up, according to a study published in The New England Journal of Medicine.

The rushed development of vaccines against COVID in 2020 marked a notable scientific achievement, with early clinical trials showing roughly 95% efficacy against symptomatic infection and nearly complete protection from severe disease, according to researchers. However, the virus has evolved significantly since then, and immunity from prior infections and vaccinations has reduced the overall severity of COVID. These changes have contributed to public uncertainty about the ongoing value of annual vaccines.

In the U.S., adult uptake of the 2024-2025 vaccine stalled at around 21% by late December 2024—half the uptake of the influenza vaccine during the same period and the lowest since COVID vaccines became available.

According to the CDC, age is the strongest risk factor for severe COVID outcomes, with the risk of death increasing sharply with age. Adults 50 to 64 face 25 times the risk of death compared with those 18 to 29, while the risk rises to 60 times for ages 65 to 74, 140 times for ages 75 to 84 and 340 times for those 85 and older.

Risk is also higher for those with certain chronic conditions and for residents of long-term care facilities, who make up less than 1% of the population but account for more than a third of COVID deaths.

Policymakers and health experts have questioned whether updated vaccines continue to provide meaningful protection in this new landscape. To address this, researchers turned to the Department of Veterans Affairs (VA) electronic health care databases to evaluate the effectiveness of the 2024–2025 COVID vaccine.

The study included 295,971 VA patients aged 18 and older who had prior care within the VA system and received the 2023–2024 COVID vaccine. Participants were followed for six months to assess three primary outcomes—COVID-related emergency department visits, hospitalizations and deaths. Baseline characteristics and time-varying factors, including demographics, health conditions and prior health care use, were used to balance the two groups and account for potential confounding.

Inverse-probability weighting and censoring techniques adjusted for differences in vaccination timing and subsequent COVID vaccine receipt, and vaccine effectiveness was estimated using weighted generalized estimating equations.

The study included 164,132 veterans who received the 2024–2025 COVID vaccine and 131,839 who did not. After accounting for demographic and clinical differences between groups, researchers found that vaccination was associated with lower risks of COVID-related outcomes over six months.

Vaccine effectiveness was estimated at 29% for emergency department visits, 39% for hospitalizations and 64% for deaths, with small absolute risk reductions per 10,000 people. Effectiveness against all three outcomes combined was 28%, but protection decreased over time, falling to about 21% after four to six months.

The study found benefits across all age groups—under 65, 65 to 75 and over 75—and among those with long-term health conditions such as heart, brain, kidney and lung disease. The results were also consistent for those with strong or weakened immune systems. Additional analyses supported these findings, suggesting the results were reliable and not likely due to other unmeasured factors.

Based on the overall methods and results, study strengths included its large veteran cohort, detailed VA electronic health records and an active-comparator design that minimized bias.

Limitations exist as well. Due to the study being observational, it can’t prove that the vaccine directly resulted in lower risks. Most participants were older White men, so findings may not apply to everyone.

The authors recommend looking at the results based on each person’s risk, noting that the overall reduction in COVID risk was small, and considering ways to make the vaccine protection last longer.