AROUND 90 per cent of those tested as part of the sixth serological survey in Delhi have Covid antibodies, official sources said Wednesday.
The latest sero survey was conducted in the last week of September, and a total of 28,000 blood samples were collected from all the 280 civic wards.
Sero positivity shows the presence of antibodies in samples, and the last such survey in Delhi, conducted in January, showed a rate of 56 per cent.
While sero prevalence is usually indicative of the infection rate, officials said the high percentage in Delhi could also be due to the “robust” vaccination numbers (see table).
“We cannot say that 90% of the people who have been tested have contracted the infection since we also have to account for vaccination. Delhi’s vaccination numbers are very robust. But it is also true that the second Covid wave had a devastating impact in Delhi and almost every family was affected. In two months (April and May), the city recorded around 7.5 lakh cases and 13,000 deaths,” an official said.
Over the past three months, the Covid situation in Delhi has improved significantly. Cases reported in a day have remained under 100 since August and the average positivity rate below 0.1 per cent.
The average number of people tested per day was around 70,000 till September, and about 55,000 in October. On Wednesday, 38 Covid cases were reported at a positivity rate of 0.06% — over 59,000 tests were conducted and no deaths were reported.
Sero surveys in other cities, conducted after the second wave and vaccination drives, also show high sero prevalence.
In the survey conducted in Mumbai in August, the prevalence of Covid antibodies was 86.64 per cent. The rate was 80.2 per cent in a survey started in Chandigarh in July, and 78.3 per cent in the one conducted in Haryana’s Gurgaon in September.