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Trend in excess winter mortality (EWM) in the USA from 1960 to 2020, with and without correction for the effect of influenza vaccination. Vaccine effectiveness before 2003/04 estimated at 40%, actual VE values for 2003/04 onward [54]. Percent elderly vaccinated increases from around 15% in the early 1960s [28] rising to 67% to 70% from 2001 onward [29,30,31,32,33].
