A lower level and a higher negative rate of SARS‐CoV‐2 IgG antibody were observed in the younger convalescent patients than the elder convalescent patients. (A) Dynamics of SARS‐CoV‐2 IgM antibody level in convalescent COVID‐19 patients in different ages. All convalescent patients were divided into eight groups (21–25, 26–30, 31–35, 36–40, 41–45, 46–50, 51–55, and 56–66) according to age. (B) Dynamics of SARS‐CoV‐2 IgG antibody level in convalescent COVID‐19 patients in different ages. Black horizontal dotted line represented 60 AU/ml. (C) The levels of SARS‐CoV‐2 IgG antibody level in younger (under or equal 35 years old, n = 251) and elder (over 35 years old, n = 287) convalescent COVID‐19 patients. (D) The percentage of convalescent patients with SARS‐CoV‐2 IgG antibody negative and IgG antibody positive. Data are expressed as mean ± SEM and analyzed by one‐way ANOVA followed by Dunnett's test (B) or Mann–Whitney U test(C). *p < 0.05, **p < 0.01, ***p < 0.001. ANOVA, analysis of variance; COVID‐19, coronavirus disease 2019; IgG, immunoglobulin G; IgM, immunoglobulin M; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2