Delhi second sero-survey: All you need to know

Doctors and epidemiologists conduct seroprevalence surveys to map the outbreak of a pandemic in a particular city or a region.

The results of the second serological survey conducted in Delhi were announced by Delhi health minister Satyendar Jain on Thursday. The results showed that there has been a six percent increase in terms of prevalence of antibodies among the city’s inhabitants. The earlier survey revealed that 22.86% of the population have developed antibodies but the second survey results show the number has reached 29% now.

A health worker seen behind a protective screen during a sample collection drive for coronavirus testing, at Shastri Park Dispensary, in New Delhi. (Raj K Raj/HT PHOTO)

Doctors and epidemiologists conduct serological surveys to map the outbreak of a pandemic in a particular city or a region. The surveys provide insights to the researchers about the ability of a region’s inhabitants to produce antibodies and what measures to undertake to curb the contagion. This also indicates whether residents of a particular city or a region are headed towards achieving ‘herd immunity’ from a disease.

The second serological survey was undertaken between August 1 to August 7 and the sample size was 15,000. The National Center for Disease Control (NCDC) and the government of Delhi had conducted the first serological survey between June 27 to July 10 with a sample size of 21,387.

For the serological survey, participants are asked to give their blood samples and then it is tested for immunoglobulin (IgG) antibodies and infections using ICMR-approved ELISA testing.

The second serological survey results also highlighted that the city could be headed towards ‘herd immunity’ but Delhi health minister Satyendar Jain remained sceptical and pointed out that experts put the number around 40%.

The survey results outlined that certain districts are developing antibodies faster than the others. Delhi’s southeast district saw prevalence of antibodies go up by almost 11% but southwest Delhi’s inhabitants have not shown any remarkable increase in antibodies.

Also, people aged below 18 years and above 50 years have higher prevalence of antibodies compared to people in the age group of 18-50 years. The survey also highlighted that women in the city have a higher antibody prevalence compared to men.

Several other cities in India have conducted serological surveys to map the growth of coronavirus among the people living in the city. Pune saw more than 51% of its population have developed antibodies. Mumbai conducted a serological survey in three slums and saw that 57% of the sample population have developed antibodies. Bihar, Haryana and Chhattisgarh are among the states who will start the second-phase of their serological surveys.