Longitudinal Assessment of Anti-Severe Acute Respiratory Syndrome Coronavirus 2 Immune Responses for Six Months Based on the Clinical Severity of Coronavirus Disease 2019

Background There is insufficient data on the longevity of immunity acquired after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Methods We aimed to evaluate the duration of SARS-CoV-2-specific humoral and cellular immunity according to the clinical severity of coronavirus disease 2019 (COVID-19). The study population comprised asymptomatic (n = 14), symptomatic/nonpneumonic (n = 42), and pneumonic (n = 41) patients. Results The anti-SARS-CoV-2 immunoglobulin class G and neutralizing antibody (NAb) titers lasted until 6 months after diagnosis, with positivity rates of 66.7% and 86.9%, respectively. Older age, prolonged viral shedding, and accompanying pneumonia were more frequently found in patients with sustained humoral immunity. Severe acute respiratory syndrome coronavirus 2-specific T-cell response was strongly observed in pneumonic patients and prominent in individuals with sustained humoral immunity. Conclusions In conclusion, most (>85%) patients carry NAb until 6 months after diagnosis of SARS-CoV-2 infection, providing insights for establishing vaccination strategies against COVID-19.