Secondary attack rate of COVID-19 among contacts and risk factors, Tamil Nadu, March-May 2020: a retrospective cohort study.

OBJECTIVE: To describe the characteristics of contacts of patients with COVID-19 case in terms of time, place and person, to calculate the secondary attack rate (SAR) and factors associated with COVID-19 infection among contacts. DESIGN: A retrospective cohort study SETTING AND PARTICIPANTS: Contacts of cases identified by the health department from 14 March 2020to 30 May 2020, in 9 of 38 administrative districts of Tamil Nadu. Significant proportion of cases attended a religious congregation. OUTCOME MEASURE: Attack rate among the contacts and factors associated with COVID-19 positivity. RESULTS: We listed 15 702 contacts of 931 primary cases. Of the contacts, 89% (n: 14 002) were tested for COVID-19. The overall SAR was 4% (599/14 002), with higher among the household contacts (13%) than the community contacts (1%). SAR among the contacts of primary cases with congregation exposure were 5 times higher than the contacts of non-congregation primary cases (10% vs 2%). Being a household contact of a primary case with congregation exposure had a fourfold increased risk of getting COVID-19 (relative risk (RR): 16.4; 95% CI: 13 to 20) than contact of primary case without congregation exposure. Among the symptomatic primary cases, household contacts of congregation primaries had higher RR than household contacts of other cases ((RR: 25.3; 95% CI: 10.2 to 63) vs (RR: 14.6; 95% CI: 5.7 to 37.7)). Among asymptomatic primary case, RR was increased among household contacts (RR: 16.5; 95% CI: 13.2 to 20.7) of congregation primaries compared with others. CONCLUSION: Our study showed an increase in disease transmission among household contacts than community contacts. Also, symptomatic primary cases and primary cases with exposure to the congregation had more secondary cases than others.

Economic Evaluation of Implementing a Rapid Point-of-Care Screening Test for the Identification of Hepatitis C Virus under National Viral Hepatitis Control Programme in Tamil Nadu, South India.

INTRODUCTION: Viral hepatitis is a crucial public health problem in India. Hepatitis C virus (HCV) elimination is a national priority and a key strategy has been adopted to strengthen the HCV diagnostics services to ensure early and accurate diagnosis. METHODS: To conduct an economic evaluation of implementing a rapid point-of-care screening test for the identification of HCV among the selected key population under the National Viral Hepatitis Control Programme in Tamil Nadu, South India. Economic evaluation of a point-of-care screening test for HCV diagnosis among the key population attending the primary health care centers. A combination of decision tree and Markov model was developed to estimate cost-effectiveness of point-of-care screening test for HCV diagnosis at the primary health care centers. Total costs, quality-adjusted life years (QALYs) of the intervention and comparator, and incremental cost-effectiveness ratio (ICER) were calculated. The model parameter uncertainties which would influence the cost-effectiveness outcome has been evaluated by one-way sensitivity analysis and probabilistic sensitivity analysis. RESULTS: When compared to the tertiary level diagnostic strategy for HCV, the point-of-care screening for selected key population at primary health care level results in a gain of 57 undiscounted QALYs and 38 discounted QALYs, four undiscounted life years and two discounted life years. The negative ICER of the new strategy indicates that it is less expensive and more effective compared with the current HCV diagnosis strategy. CONCLUSIONS: The proposed strategy for HCV diagnosis in the selected key population in Tamil Nadu is dominant and cost-saving compared to the current strategy.