Delhi’s sero-prevalence remains same, report calls for another round of survey

The report suggests that the next round of sero survey be conducted in June-end or July-beginning to capture the exposure to infection during the massive second wave that saw Delhi reporting over 28,000 cases in a day

Delhi’s latest sero survey shows that the population-level prevalence of antibodies in the city was at 56.09%, almost the same as that of the January round, said officials. The survey, however, is not comparable to the earlier one, which found the sero-prevalence to be 56.13%, as sample collection had to be cut short this time amid rising Covid-19 cases mid-April.

Representational Image. (HT archive)

The report, submitted to the government last Monday, hasn’t officially been released yet.

The report by researchers from Maulana Azad Medical College also suggests that the next round of sero survey be conducted in June-end or July-beginning to capture the exposure to infection during the massive second wave that saw Delhi reporting over 28,000 cases in a day.

For the April round, around 13,000 samples were collected instead of the proposed 28,000; and from just 141 of Delhi’s 272 wards. To make it comparable, researchers will have to go through the data from these 141 wards from the previous round of the survey.

“The survey had to be stopped midway because cases started rising and a lockdown was implemented. Now, the samples that were collected during the five or six days that the survey was carried out are being analysed,” a Delhi government official had told HT earlier. The sample collection for the sixth round began on April 12, just a day after the city reported over 10,000 cases in a day for the first time, and was stopped once the government announced a lockdown on April 19.

The reports of the antibody testing are yet to be shared with the study participants.

“The dates for the next round of sero survey haven’t been confirmed yet,” said an official from Delhi’s health department.

When the first sero survey was conduced in June-end last year, 22.6% of the 21,000 people sampled had antibodies. This shot to 29.1% of the 15,000 people sampled in August, and then dropped to 25.1% among the 17,000 people sampled in September (due to a change in methodology and dropping antibody levels in the population, the researchers said). In October, it went up to 25.5% in a sample size of 15,000.