THE FIFTH serological surveillance round conducted in Delhi indicated that more than 50 per cent of people have developed antibodies against Covid.
This is the highest seroprevalence observed since the Covid outbreak, suggesting that the city is moving closer to achieving herd immunity.
“The prevalence in one district is around 58 per cent, which clearly shows that a large number of individuals have developed antibodies to the virus,” a senior government official said. As part of the survey that ended Friday, the authorities collected 28,840 samples, the most during such an exercise in Delhi so far.
Only Pune has reported a prevalence of more than 50%, but that was several months ago. Seroprevalence tests in several other cities have shown antibodies in between 30 and 40 per cent of respondents.
As new case identification has decreased over the past four months, some experts and scientists suspect that a far higher proportion of the population might already have been infected. The proof is provided by the findings of the Delhi serosurvey.
The first such survey conducted by the Delhi government in August last year found that 29.1 per cent had antibodies. In September, the figure fell to 25.1 per cent and stood at 25.5 per cent in October. A serosurvey was also performed by the National Centre for Disease Control (NCDC) in July, where antibodies were found in 23% of those surveyed.
The new survey began on January 11 in Delhi and samples were sent for testing to the Institute of Liver and Biliary Sciences (ILBS) and an initial report was sent to Delhi Health Minister Satyendar Jain’s office.
Is Delhi approaching herd immunity?
The survey “shows that there have been many asymptomatic infections in the city and we are approaching herd immunity,” Dr Shobha Broor, former head of microbiology at AIIMS told The Indian Express.
In the next round, the figure could go up to 70 per cent as more citizens would have been vaccinated by that time. In any case, the presence of antibodies would not impact the ongoing vaccination campaign. Those who have developed antibodies should go ahead and take the shot as the injection will improve the reaction further,’ she said.
Dr Neeraj Nischal, Associate Professor at AIIMS, Department of Medicine, told The Indian Express that the high prevalence of antibodies may help to contain the pandemic further.
“It indicates that a lot of asymptomatic infections, which were not reported at the time, occurred during the pandemic. As approximately 50% have formed antibodies against the virus, this is our normal way of gaining herd immunity. This, combined with the ongoing vaccination campaign, will help achieve herd immunity, and it will be easier than anticipated to contain the pandemic,” Dr Neeraj added.
The aim of a serological survey is to verify the prevalence of a disease in a population by detecting the existence of unique antibodies to the virus. Serological examinations are carried out to detect illnesses and autoimmune disorders. It can also be carried out to check whether a person has acquired immunity to certain illnesses.