Figure 1.

Study enrollment. One hundred ninety-seven participants were screened, with 65 (33%) having hemagglutination inhibition titers ≥1:40, making them ineligible for the study. A total of 49 participants were enrolled. Eight were excluded prior to challenge. Forty-one participants were inoculated with 1 of 4 doses of influenza A(H3N2). Four were excluded due to infection with another respiratory virus, resulting in a total of 37 participants included in the analysis. Abbreviations: echo, echocardiogram; HAI, hemagglutination inhibition; PFT, pulmonary function test; TCID₅₀, 50% tissue culture infectious dose.