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Because of regular viral drift, influenza vaccine effectiveness and illness severity are variable. In addition, due to social distancing for Covid-19 during the 2020–2021 flu season, influenza circulation was unusually low. To assess the effectiveness of the flu vaccine after the Covid-19 pandemic, researchers examined vaccine surveillance data on nearly 20,000 children (6 months to 17 years of age) who received care for an acute respiratory illness at seven U.S. medical centers over three influenza seasons from 2021 to 2024.
Overall, 14% of the children tested positive for influenza and 43% of the children were vaccinated.
Vaccine effectiveness against influenza-associated hospitalizations and outpatient visits was 55% acro…