Annual flu shots work worse the second year: https://www.cidrap.umn.edu/news-perspective/2014/11/study-adds-more-data-effects-consecutive-year-flu-shots https:

Annual flu shots work worse the second year: https://www.cidrap.umn.edu/news-perspective/2014/11/study-adds-more-data-effects-consecutive-year-flu-shots https://www.cidrap.umn.edu/news-perspective/2014/11/study-ad...