The state health department released the serosurvey report of phase III from July 2021 on Saturday. The overall prevalence in the State was about 66.2 percent, with 26,610 samples tested, 17,624 individuals had IgG antibodies against the SARS-CoV-2 Virus.
While the highest seropositivity was found in Virudhunagar which was about 84 percent, the lowest seropositivity of 37 percent was reported in Erode. Chennai reported a seropositivity of about 82 percent.
The report mentioned that the increase in the overall seropositivity can be attributed to Serosurvey Phase III being conducted during the declining phase of the COVID-19 second wave in Tamil Nadu. The vaccination coverage in the State is also a contributing factor, with 97.6 lakh people getting either single or double dose upto June in the State.
The western districts like Erode, Coimbatore, and Tiruppur have reported around 45 percent seropositivity which could be attributed to the consistent reporting of new COVID-19 cases in these districts.
As part of phase 3 sectional serosurvey, a total of 888 Clusters were included covering 26,610 samples and tested for the presence of SARS CoV-2 IgG antibodies using Chemiluminescence based Immuno Assay (CLIA).
Each cluster consists of 30 participants drawn randomly from a village in a rural area or a street in the case of an Urban area. All the samples were tested at six referral labs of the Directorate of Public Health and Preventive Medicine located in Chennai, Trichy, Madurai, Coimbatore, Tirunelveli, and Salem for the detection of IgG antibodies.
Health Minister Ma Subramanian released the report in the presence of health Secretary J Radhakrishnan and Director of Public Health and Preventive Medicine Dr T S Selvavinayagam.
In the previous sero-surveys held in October 2020 and April 2021, a seropositivity of about 31 percent and 29 percent was observed respectively.