Does heterogeneity define COVID-19 transmission – sero-epidemiological survey data from a Central Indian urban settlement
Relaxation of mass quarantine (lockdown) measures has led to an increase in the daily positivity rate of SARS-CoV-2. However, the pattern and dynamics of its spread has been heterogenous across and within the states of India. This sero-epidemiological prevalence survey conducted in the city of Ujjain is one of the earliest such studies conducted to understand the determinants and dynamics of spread of COVID-19 in Ujjain and similar cities of Madhya Pradesh. A total of 4,883 individuals chosen through a stratified multi-stage random sampling method, were approached to capture socio-demographic information and any history of symptoms associated with COVID-19. A sample of venous blood was also collected and assessed for the presence of SARS-CoV-2 specific antibodies using the Electrochemiluminescence Immunoassay (ECLIA) technique. Overall unadjusted sero-prevalence for anti-SARS-CoV-2 antibody was found to be 14.2% (95% CI: 13.2% - 15.2%), and adjusted sero-prevalence was found to be 13.9% (95% CI: 10.4% - 18%). The adjusted sero-prevalence was highest in the age-group between 30 and 45 years (17.1%) and was lowest in children <15 years (9.5%). Sero-positivity was significantly higher in males (p=0.006) and in the 30-45 years age group (p=0.009). Adjusted titre values for anti-SARS-CoV-2 antibody were found to be 10.4 COI (SE = 3.38 COI) for the High Burden tertile; 4.8 (SE = 1.34 COI) for the Intermediate Burden tertile; and 6.1 COI (SE = 2.19 COI) for the Low Burden tertile.