CHENNAI: The Sero Survey II, conducted by the Directorate of Public Health in April this year, showed that 23 per cent of people had SARS-CoV-2 antibodies. In Sero Survey I, which was conducted in October-November, 2020, the seropositivity was 31 per cent.
The new survey report, which was shared with the media by the Health Department, showed that of the 22,904 people tested for antibodies against SARS-CoV-2, a total of 5,316 people had them. The highest seropositivity was found in Tiruvallur district (49 per cent), and the lowest in Nagapattinam (9 per cent).
The samples were collected from 765 clusters, with 30 participants randomly selected from a village in rural areas, or a street in urban areas. The sero survey was conducted in all districts except Chennai. The report also said various coronavirus variants, including B.1.617.2 (Delta), were detected in Tamil Nadu. Sero Survey III is planned in July-August, the report said.
The reason for the decline in seropositivity compared to Sero Survey I could be the timing of the survey, waning of antibodies, vaccination coverage, and emergence of SARS-CoV-2 variants, the report said.
Fast facts
According to Sero Survey II, of the 22,904 people tested for antibodies against SARS-CoV-2, a total of 5,316 people had them