The seventh round of the serological prevelance survey that seeks to find presence of antibodies against COVID-19 began in the national capital on Friday, amid lower number of coronavirus cases being reported in the city for the past several weeks.
The previous survey (sixth in the series), was conducted a few months ago, starting April 12, when Delhi had been reeling under the brutal second wave of the pandemic.
Sources said the seventh serological survey began on Friday. However, they did not specify the timeline of the exercise.
About 28,000 samples are expected to be taken as part of the survey, another source said, adding that vaccination history will also be taken from participants.
Also, the exercise is taking place at a time when a large segment of the population has been vaccinated against COVID-19.
Delhi's population is over two crore, spread across 11 districts.
A total of 1.76 lakh doses, including 86,634 first shots and 89,588 second jabs, were administered on September 22, according to the city's vaccination bulletin issued on Thursday.
Over 1.65 crore doses have been administered till date, it said, adding that it includes over 1.1 crore first doses in total and over 50 lakh second doses.
The outcome of the fifth round of sero-prevalance survey had found that the prevalence was over 50 per cent, indicating then that Delhi population might have been heading towards attaining herd immunity against the coronavirus infection.
As part of the survey, which had ended around January 21, samples were collected from over 25,000 people from various districts across the city.
Experts say herd immunity is said to have been developed in a population segment, if 50-60 per cent of those are found to have the presence of antibodies in a sero-prevalance survey.
Herd immunity implies that in any set of people in a community, after becoming infected by the virus, a lot many of them become immune it on account of antibodies developed in response to it. And, hence, such people become a protective layer between an infected person and uninfected people, thereby breaking the chain of viral transmission.
The first sero-prevalance, done last year from June 27-July 10 by the Delhi government in association with the National Centre for Disease Control (NCDC), had used 21,387 samples and found that around 23 per cent of the people surveyed had an exposure to the novel coronavirus.
The exercise in August 2020 showed 29.1 per cent people had antibodies.
In the surveys in September and October, last year, the figures stood at 25.1 per cent and 25.5 per cent in October.
The exercises have been undertaken for a comprehensive assessment of the COVID-19 situation in Delhi and to formulate strategies based on its findings.
Delhi on Friday recorded zero deaths due to COVID-19 and 24 fresh cases, as the positivity rate dropped to 0.03 per cent, according to data shared by the city health department.
The deaths due to the coronavirus infection in Delhi stand at 25,085, according to official figures.
The number of cumulative cases on Friday stood at 14,38,658. Over 14.13 lakh patients have recovered from the virus, according to the latest health bulletin.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)