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Level of humoral (A) and cellular (B) immunity in study participants exposed to the viral antigen less than six months prior than those exposed more than six months prior. Levels of humoral (C) and cellular (D) immunity in different age groups show age-dependent differences in distribution. In Figure 2A,B, study participants were divided into two groups, with an arbitrary limit of 6 months. *—p < 0.05 (Mann–Whitney); **—p < 0.001 (Mann–Whitney).
