Over 23% Delhi residents have Covid-19 antibodies, shows sero-survey

Medics prepare to collect samples for swab tests from a Covid-19 mobile testing van at Ramakrishna Mission area in New Delhi. (PTI Photo/Manvender Vashist)
A sero-surveillance study done in Delhi found that 23.48 per cent of the city's respondents had IgG antibodies, indicating many people would likely be infected with coronavirus but asymptomatic. The study was conducted by the National Center for Disease Control (NCDC) in collaboration with the Delhi government from June 27 to July 10.

A total of 21,387 samples were collected according to lab standards and then tested. These tests were not diagnostic but done to identify the presence of antibodies in the general population. Antibody testing done repeatedly over time generates important evidence for assessing the spread of the pandemic from time to time.

Survey teams were set up for all 11 districts of Delhi and blood samples were collected from select individuals after taking written informed consent. The sera so collected were then tested for IgG antibodies and infection using Covid KAVACH ELISA, approved by Indian Council for Medical Research (ICMR).

This was one of the largest sero-prevalence studies conducted in the country using the ELISA testing.

Notably, the study indicated that a large number of infected persons remained asymptomatic. This implies the following:

1. Nearly six months into the epidemic, only 23.48 per cent of the people are affected in Delhi, which has several pockets of dense population. This can be attributed to the proactive efforts taken by the government to prevent the spread of infection, including a prompt lockdown, effective containment and surveillance measures like contact tracing and tracking, as well as citizen's compliance to appropriate Covid-19 behaviours.

2. However, a significant proportion of the population is still vulnerable. Therefore, containment measures need to continue with the same rigour. Non-pharmacological interventions like physical distancing, use of face mask/cover, hand hygiene, cough etiquette and avoidance of crowded places, must be followed strictly.

According to the health ministry data, Delhi's Covid-19 caseload on Tuesday increased to 123,747, and the death toll rose to 3,663.

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