What is the problem and what is known about it so far?
Safety studies of the original COVID-19 vaccine found infrequent but widely reported adverse events. In recent years, the COVID-19 vaccine has been updated several times, which may change the risk for adverse events in the United States, where most of the population has acquired some immunity to COVID-19.
Why did the researchers do this particular study?
The authors wanted to examine risks for adverse events within 90 days after receipt of 3 newer types of COVID-19 vaccines, along with the influenza vaccine, in comparison with receipt of only the influenza vaccine.
Who was studied?
The study used data from the U.S. Department of Veterans Affairs electronic medical records to identify persons who received COVID-19 and seasonal influenza vaccines at the same visit or received only the influenza vaccine between September 1, 2022, and August 26, 2025.
How was the study done?
This study simulated (or emulated) a randomized trial using real-world data and analytic methods to compare adverse events after COVID-19 plus influenza vaccines versus only the influenza vaccine. During the study time frame, 12,344,082 veterans had a primary care visit; after exclusions such as a recent COVID-19 infection or documented refusal, 2,518,329 veterans who received the influenza vaccine were studied, of whom 705,124 received both vaccines and 1,813,205 received only the influenza vaccine. Analytic methods were used to balance these 2 study groups. Each veteran could be studied up to 3 times when different updated COVID-19 vaccines were offered: 2022 to 2023, 2023 to 2024, and 2024 to 2025. The authors examined 46 adverse events occurring within 90 days and grouped them by severity.
What did the researchers find?
For the 2 more severe categories of adverse events, the risks were similar for the 3 updated types of COVID-19 vaccines when given with the influenza vaccine compared with only influenza vaccination. For the less severe group of adverse events, there was a small increase in syncope (fainting) and a small decrease in tinnitus (ringing in the ears), but these risks were not statistically significant.
What were the limitations of the study?
This was not an actual randomized trial, so there may be unmeasured factors that could have affected outcomes. Most study participants were men.
What are the implications of the study?
The study found that the short-term risks for adverse events were similar for persons receiving both COVID-19 and influenza vaccines compared with the influenza vaccine alone. This study offers reassurance about the safety of receiving the newer COVID-19 vaccines with the influenza vaccine at the same time.
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