Life course exposures continually shape antibody profile and risk of seroconversion to influenza

Bingyi Yang; Justin Lessler; Huachen Zhu; Chaoqiang Jiang; Jonathan M. Read; James A Hay; Kin On Kwok; Ruiyin Shen; Yi Guan; Steven Riley; Derek A.T. Cummings

Across our cohort, changes, particularly increases, in titer were seen across all strains, including strains that have long been extinct (Fig. 2 C and F and Fig. 4A) . 97.9% of people experienced a rise against one or more strains. 73.7% showed a 4-fold or greater titer increase (seroconversion) to one or more ( Fig. 2I) , with increased risk of occurring in strains circulating after 1998 compared to A/HongKong/1968 [odds ratio (OR) ranges from 2.7 (95% CI, 2.0 to 3.9) to 16.4 (95% CI, 12.0 to 22.6 ) across these strains] ( fig. S4 ), i.e. strains more antigenically similar to ones with which the participant could have been infected;. The largest increases in HAI titers were detected for four recent strains (Fig. 4B) , and there was high-correlation in seroconversions; 63.1% of those who seroconverted to one or more strains seroconverted to all four strains. (fig. S5 ). Meanwhile, a minority of people (18.3%) showed a decrease in titer to one or more strains, likely due to transient boosting from exposures prior to baseline sampling (5, 18) .