Chennai: About 88 per cent of adults and 68 per cent of children above the age of 10 in Tamilnadu have antibodies against Covid-19, the fourth serosurvey conducted in the last week of December showed.
Serosurvey in October-November showed seropositivity of 32 per cent among the people of Tamilnadu, 29 per cent in April 2021, and 70 per cent in July-August 2021.
At the time of the survey, vaccination had not begun for those under 18 years, yet many children had detectable levels of antibodies. ‘These people have acquired antibodies against natural infection,’ said Director of Public Health Dr TS Selvavinayagam.
According to the data shared by the Health Department, the sero-prevalence which was at 32 per cent in November 2020 (first sero survey) dropped to 29 per cent in April 2021 (second sero survey) and again surged to 70 per cent in August 2021 (third sero survey).
‘In December 2021, it grew to 87 per cent,’ the findings said. A 30-member team was formed into 1,076 groups which examined 32, 245 people in rural and urban areas for the study. Accordingly, the sero-prevalence among the people aged above 18 grew to 87 per cent, it said.
The survey, however, does not cover reinfections as it had been carried out before the Omicron-fuelled third wave, he said. ‘But data from another study showed high hospitalizations, complications, and deaths among people whowere unvaccinated. This was particularly high among the elderly and people with comorbid conditions such as uncontrolled diabetes and hypertension.’
The seropositivity was highest in Tiruvarur (93 per cent) and 88 per cent in Chennai. In mid-January, 97 per cent of the cases in Tamilnadu were that of the Omicron variant. Until 7 December, all cases were of Delta variant.