摘要：Background: The utility of antibody tests in policy making is limited to seroprevalence surveys. World Health Organisation has stated that recovered people have antibodies to SARS-CoV-2. Convalescent serum contains antibodies that can neutralize the virus in cell cultures and IgG is both a marker for viral exposure and an indicator of recovery. We undertook this study to report immune response as a return to work strategy in a containment zone of 757 adults from a working mens’ hostel. Methodology: The individuals were divided into three cohorts. Cohort-A comprised of RTPCR confirmed cases, Cohort-B comprised of those who were admitted as suspects but were negative in Rt-PCR test and Cohort-C were those, who remained asymptomatic. We studied the clinical features and undertook a qualitative antibody test of all adult males from the hostel after transmission of the disease was assumed to be over in the containment zone. Result: Dry cough, sore throat and fever were the most common presenting symptoms. (Fig 1). On serology testing, 47/87 (54.04%) tested IgG positive from Cohort A and 25/74 (32.05%) individuals were IgG positive from Cohort B with a significant statistical difference (p<0.05). There were 176 (29.72%) individuals who were IgG positive from Cohort C (Table 1), who remained asymptomatic. We found the seroconversion rate to IgG to be 67.85% (19/28) in symptomatic confirmed cases [OR 2.50 (0.97-6.43)]. None of the subjects tested positive for IgM. Conclusion: We found around half of the confirmed cases to seroconvert to IgG and antibodies were not detected in the rest. The utility of the test in return to work decision is therefore, debatable. The study found almost 30% of the unconfirmed individuals to have seroconverted, indicating presence of asymptomatic transmission. Preventive measures of social distancing, wearing of masks alongwith well ventilated offices with adequate air exchange mechanisms would be the future strategy for work place functioning.
关键词：Antibody testing; asymptomatic transmission; COVID; return to work; seroconversion
