Figure 2From: Challenge of conducting a placebo-controlled randomized efficacy study for influenza vaccine in a season with low attack rate and a mismatched vaccine B strain: a concrete example Incidence of solicited injection site symptoms during the first four days following vaccination (Total cohort subset for reactogenicity; trivalent inactivated split virus influenza (TIV) N = 640, Placebo N = 320).Back to article page