To study heterogeneity in SARS-CoV-2 IgG response titre in patients recovered from COVID-19

The COVID-19 pandemic caused a serious health challenge to the entire mankind. The association between clinical characteristics of disease and formation of neutralizing antibodies have not well studied. A prospective study was conducted for patients recovered from confirmed SARS-CoV-2 infections from 1^st August 2020 to 28^th February 2021, to study the association between SARS-CoV-2 IgG antibody response titres and clinical characteristics of the disease. A total 92 patients were included in the study. Median age was 52 years; majority were male and middle or old aged.  About 48% patients required hospitalization and 38.3% had moderate CT severity score. Positive SARS-CoV-2-IgG was detected in all patients except one. On comparing the antibody titres among various sub-groups of COVID-19 recovered patients, old age was the only factor associated with statistically significant higher antibody response (28 AU/ml for age<35 years, 53 AU/ml for age group 35-60, and 71 AU/ml for age group >60 years, p=0.01). Severity of infection, worse CT severity scores, need of hospitalization, oxygen or ventilatory support were associated with higher antibody titres but were not statistically significant. There was a strong correlation of antibody titres when analysed for age of study population (Spearman correlation=0.39, p<0.001); whereas a weak correlation (Spearman correlation=0.03, p=0.753) was seen when analysed for CT severity score. Elderly patients had higher antibody titre after recovery from Covid-19 infection. Severity of disease, need of hospitalisation or oxygen/mechanical ventilation did not influence the antibody titre.