Covid-19: Sample collection for Delhi’s second sero-surveillance ends

The survey will indicate what percentage of the city’s population has developed antibodies against the Sars-Cov-2 virus, which causes Covid-19, since the first such survey was conducted between June 27 and July 10.

Collection of blood samples for the second round of serological surveillance in Delhi was completed on Friday, with administrations of the city’s 11 districts collecting samples from just over 15,000 people, intended to be representative of the Capital’s population.

The highest number of samples were collected from Northwest district, followed by West, and Central. (Sonu Mehta/HT Photo)

The results of the survey are expected early next week, officials said.

“The results will be processed by a team at Maulana Azad Medical College, and are likely to be released by next week,” officials from Delhi’s health department said.

The survey will indicate what percentage of the city’s population has developed antibodies against the Sars-Cov-2 virus, which causes Covid-19, since the first such survey was conducted between June 27 and July 10. Of those surveyed in that instance, 22.6% had antibodies against the infection.

The highest number of samples were collected from Northwest district, followed by West, and Central.

“We have been reporting new cases of the infection since the previous sero-surveillance, meaning that the proportion of people who have the antibodies are likely to be higher this time around. If 30 to 60% of the population has the antibodies, it will show that Delhi is on its way to developing herd immunity,” said a senior doctor from central district, on the condition of anonymity.

Herd immunity is said to have been achieved when a significant proportion of the population has developed resistance to an infection, preventing its further spread.

The results of the survey are, however, unlikely to change on-ground strategies, officials said.

“We have to continue testing heavily, especially in areas that are reporting more cases, trace contacts of the infected persons, and isolate everyone to prevent the spread of the infection. Even if a high proportion of the people develop antibodies, we cannot relax containment measures right now,” said an official from the north district, which finished sample collection on Friday.

“ In the month since Delhi’s first survey, I am expecting that the prevalence of antibodies must have gone up to about 40%,” said Dr Jugal Kishore, head of the department of community medicine at Safdarjung hospital.

The government had announced on July 22 that a serological survey will be conducted during the first five days of every month to keep tracking the progress in the antibody levels.