Study design
The present study was approved by the Institutional Ethics Committee of Dr D Y Patil Vidyapeeth (Ref No-DYPV/EC/634/2021 dated 25 February 2021) and recruited hospitalized patients with COVID-19 during March 2021 to February 2022 at Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pune. The participants were ≥18-years-old male and female subjects who provided written informed consent before enrolment. The study was carried out in compliance with good clinical practices, including the International Conference on Harmonization Guidelines and the Declaration of Helsinki. COVID-19 patients were enrolled into the study during the period of hospitalization and the first blood samples were drawn for immunological investigations, which was followed by two additional samples collected at 1 month and 6-8 months, respectively after inclusion in the study (Graphical Abstract).