Clinical and epidemiological characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are now widely available, but there are few data regarding longitudinal serology in large cohorts, particularly those from low-income and middle-income countries. We established an ongoing prospective cohort of 3,840 SARS-CoV-2-positive individuals according to RT-PCR in the Delhi-National Capital Region of India to document clinical and immunological characteristics during illness and convalescence. The immunoglobulin G (IgG) responses to the receptor binding domain (RBD) and nucleocapsid were assessed at 0 to 7 days, 10 to 28 days, and 6 to 10 weeks after infection. The clinical predictors of seroconversion were identified by multivariable regression analysis. The seroconversion rates during the postinfection windows of 0 to 7 days, 10 to 28 days, and 6 to 10 weeks were 46%, 84.7%, and 85.3%, respectively (N = 743). The proportion with a serological response increased with the severity of coronavirus disease 2019 (COVID-19). All participants with severe disease, 89.6% with mild to moderate infection, and 77.3% of asymptomatic participants had IgG antibodies to the RBD antigen. The threshold values for the nasopharyngeal viral RNA RT-PCR of a subset of asymptomatic and symptomatic seroconverters were comparable (P = 0.48) to those of nonseroconverters (P = 0.16) (N = 169). This is the first report of longitudinal humoral immune responses to SARS-CoV-2 over a period of 10 weeks in South Asia. The low seropositivity of asymptomatic participants and differences between assays highlight the importance of contextualizing the understanding of population serosurveys.
Members of DBT India Consortium for COVID-19 Research:
Coordinating Institute: Translational Health Science and Technology Institute (THSTI)
Coordinating Principal Investigator: Dr. Shinjini Bhatnagar
Shaheed Hasan Khan Mewati Government Medical College, Nalhar, Nuh, Haryana: Dr. Yamini
Lady Hardinge Medical College, New Delhi: Drs. Harish K. Pemde, Tanmaya Talukdar
SGT Medical college, Gurugram, Haryana: Drs. Pankaj Abrol, Mukesh Sharma
Dr. Dang’s Lab, New Delhi: Drs. Navin Dang, Manavi Dang, Arjun Dang, Leena Chatterjee, Devjani De
Acknowledgments: We thank the Department of Biotechnology, Government of India, for supporting the consortium. We are grateful to the leadership and administration of all partner institutions in the consortium for their help and support. We thank all the clinical, laboratory, and data management staff for their contributions to this work and the consortium at large. The American Society of Tropical Medicine and Hygiene has waived the Open Access fee for this article due to the ongoing COVID-19 pandemic.
Address correspondence to Shinjini Bhatnagar, Professor of Eminence and Head- Maternal and Child Health, Translational Health Science and Technology Institute, Faridabad, India, or Gagandeep Kang, Professor, The Wellcome Trust Research Laboratory, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, TN 632004, India. E-mails: email@example.com or firstname.lastname@example.orgThese authors contributed equally to this work.
Financial support: This work was supported by Department of Biotechnology, Government of India (BT/PR40401/BIOBANK/03/2020), and by the Ind-CEPI Coalition for Epidemic Preparedness Innovations (102/IFD/SAN/5477/2018-2019).