The overall prevalence of Covid antibodies has shown a “significant reduction” during the month of September among people in Delhi as compared to the data brought forth by the serosurvey conducted in August. The latest round of the survey said that Delhi’s overall seroprevalence fell from around 29% in August to 25.1% in September.
The study also found seroprevalence to be more among women than men, and people belonging to the low socioeconomic category and those living in unplanned colonies.
Participants are screened for the presence of antibodies in the blood during the serosurvey to check whether they were infected with coronavirus in the past. The surveillance is being used to check the prevalence of Covid in the community. The results and analysis of the serosurveillance of the September round in Delhi was placed before the Delhi High Court on Wednesday in a case filed by advocate Rakesh Malhotra about the Covid testing process and strategy in Delhi.
Seroprevalence ranged from 14.6% in the South West district to 31.8% in North West. There were 17,409 participants in the study across the capital, and the “fall was particularly localised” in three districts — North East, Central and North Delhi.
The third serosurvey, conducted between September 1-7, was preceded by July and August rounds. While the July round revealed a seroprevalence of around 22.86% among 21,387 participants, the August round found it to be 29.36% among 15,046 participants. August results ranged from 17.4% in South West and 33.2% in South East.
“The September round of the SARS-CoV-2 serosurvey in Delhi showed a reduction of the IgG antibody seroprevalence from 28.7% to 25.1%,” as per the findings of the serosurveillance report.
In the latest serosurveillance conducted by the doctors of Maulana Azad Medical College, it has also been found that “female gender has suffered significantly more asymptomatic SARS-CoV-2 infections as observed during all the survey rounds”. The study has also revealed that seroprevalence was highest among participants of low socioeconomic status with per-capita income of Rs 5,000 or less — 26.3% of them were found to have antibodies in September as compared to 20.5% who have income of Rs 5,000 or more.
“The presence of overcrowding also increased the risk of the SARS-CoV-2 infection. In the September round, when sampling was recommended through sample stratification as per the settlement type, the seroprevalence among participants living in planned colonies was significantly lower compared to those residing in other settlement types,” according to the findings mentioned in the serosurveillance report.
In the August round, 29.4-31.4% of women were found to have antibodies and 26.3-28.3% of men had antibodies. In September, 25.7-27.1% of women showed presence of antibodies and the same number for men was 23.5-24.7%. The seroprevalence was also found to be higher among children and the elderly.
While July and August rounds also had found that a higher number of people living in containment zones had antibodies, the seroprevalence was found to be lower in September month among the participants in containment zones, with the number coming down to 20.5% from 32.7% between August and September. The study also found that nearly one-third of the participants with a past history of Covid did not have detectable presence of antibodies, with studies showing depletion of antibodies over time.
The division bench of Justices Hima Kohli and Subramonium Prasad has ordered authorities to inform the court about the schedule for conducting the next round of serosurveillance on the next date of hearing.
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