A large Swiss study has found that recent COVID jab boosters may raise the risk of flu-like illness and work absences among healthcare workers in a post-pandemic setting.
Researchers followed 1,745 healthcare workers across nine hospitals from November 2023 to May 2024, a period of high COVID-19 transmission. Participants reported weekly on symptoms and sick leave, while their vaccination history was tracked. Using statistical models to control for confounding factors, the study found that healthcare workers who had received recent COVID-19 booster doses were more likely to experience influenza-like respiratory illness (ILI) and lose workdays, with the risk higher the more recent the vaccination.
In contrast, seasonal influenza vaccination was linked to a reduced risk of illness and work absence. The findings suggest that routine use of mRNA COVID jabs as annual boosters in low-risk healthcare populations may not provide clear short-term benefits—and could even increase illness risk shortly after administration.
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