29% Delhi residents exposed to Covid-19, have antibodies: Second serosurvey

First survey in June-July period had shown about 23% were exposed. Two more rounds of serosurvey are scheduled in first week of September and October

Nearly a third of Delhi’s population has been exposed to coronavirus, showed the second round of a serological survey, suggesting the Capital is far from reaching the herd immunity stage which is achieved when 40-50 per cent develop antibodies.

Samples for the serosurvey were taken during the first week of August and showed 29.1 per cent had developed antibodies.

The first survey, done in the June-July period by the National Centre for Disease Control, had shown approximately 23 per cent of the population was exposed to the virus. Two more rounds of serosurvey are scheduled in first week of September and October.

A gender analysis of 12,598 subjects in the follow-up survey showed that 28.3 per cent of males and 32.2 per cent of females exhibited Covid-19 antibodies, a statement by the Delhi government said.

Age-wise break-up of seroprevalence showed nearly 35 per cent of those with antibodies were less than 18 years of age. Around 29 per cent were in the age bracket of 18 to 49, while 31 per cent were above 50 years. 

Serosurvey involves collection of blood samples from a group of individuals to check them for antibodies for Covid-19. If the test is positive it shows that the person has been infected in the past.

The survey, while providing scientific guidance, shows the percentage of people who are more at risk of catching the infection and points at the areas which require more containment effort.

Coronavirus cases in Delhi stood at 156,139 on Thursday morning, according to health ministry’s data, with the daily growth in cases staying below 1 per cent in the last 10 days.

Delhi’s southeast district witnessed the sharpest rise of 50 per cent in seroprevalence, with 33 per cent of those surveyed showing antibodies. 

The highest number of people exposed to coronavirus, according to the survey, were in the north east with seroprevalence of almost 30 per cent. Though compared to the last survey, the district showed a minimum increase of around 7 per cent.  

“Multi-stage sampling was done for selection of the study participants in each ward within the communities of the catchment area of the Delhi government dispensaries and primary urban health facilities through a team consisting of local frontline health workers,” the statement said.

The Indian Council of Medical Research had earlier said that in order to study the spread of the disease multiple serosurveys will be conducted in states and the Elisa test kit for antibody detection will be made available to them.