Antibody response to inactivated COVID‐19 vaccine in patients with type 2 diabetes mellitus after the booster immunization

BACKGROUND: The immunogenicity of booster inactivated COVID‐19 vaccines in patients with type 2 diabetes mellitus (T2DM) has remained unclear. Our study aims to investigate the antibody response to inactivated COVID‐19 vaccine following booster vaccination in patients with T2DM. METHODS: A total of 201 patients with T2DM and 102 healthy controls (HCs) were enrolled. The levels of anti‐SARS‐CoV‐2 total antibodies, anti‐receptor‐binding domain (RBD)‐specific IgG, neutralizing antibody (NAb) toward SARS‐CoV‐2 wild type (WT), and NAb toward SARS‐CoV‐2 Omicron BA.4/5 subvariant were measured to evaluate the vaccine‐induced immunological responses. RESULTS: The titers of anti‐RBD‐specific IgG (p = 0.018) and inhibition rates of NAb toward WT (p = 0.007) were significantly decreased in patients with T2DM compared to HCs after booster vaccination for more than 6 months. Both HCs and patients with T2DM showed poor resistance against BA.4/5 due to the detected inhibition rates being lower than the positive threshold. The levels of anti‐RBD‐specific IgG were positively associated with the proportions of CD3(+)CD4(−)CD8(−) T cells (p = 0.045), and patients with T2DM who had anti‐RBD‐specific IgG positivity showed higher proportions of CD3(+)CD4(−)CD8(−) T cells compared to those negative (p = 0.005). CONCLUSIONS: Patients with T2DM showed impaired antibody responses after booster vaccination for more than 6 months. Decreased anti‐BA.4/5 responses give rise to the possibility of breakthrough infections for both patients with T2DM and HCs.