Early estimates on the effectiveness of this year's flu vaccines indicate they may be less effective at preventing hospitalization than in years past, based on data from South America, where the annual flu season occurs earlier.

According to a report from the Centers for Disease Control and Prevention (CDC), the flu shot appeared to be 34.5 percent effective at preventing hospitalizations this year in countries like Argentina, Brazil, Chile, Paraguay and Uruguay.

During the 2023 flu season in these same countries, the vaccine efficacy........

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