A seroprevalence study done in Hyderabad has revealed that around 54 per cent of the city's residents developed antibodies against SARS-CoV-2, indicating prior exposure to coronavirus. According to a CCMB release on Thursday, the joint study by the CSIR-Centre for Cellular and Molecular Biology (CCMB), National Institute of Nutrition (NIN) and vaccine-maker Bharat Biotech considered around 9,000 samples.
The scientists checked for antibodies against the virus in people across 30 wards of the city. Nearly 300 people from each ward, all of them older than 10 years of age, were tested, it said.
Most of the wards showed a similarly uniform range of seroprevalence, from 50-60 per cent. However, a few wards showed as much as 70 per cent or as low as 30 per cent as well.
Women showed a marginally higher seropositivity rate (56 per cent) than men (53 per cent). Those above 70 years of age showed a lower seropositivity (49 per cent), perhaps because of limited mobility and extra care taken by the older people during the pandemic, it said.
Unsurprisingly, those who had COVID-19 positive cases in their own households, showed the maximum seropositivity of 78 per cent. This was followed by those with known COVID-19 contacts outside their household (68 per cent), the release said.
"This multistage random sampling study on 9,000 people in the city of Hyderabad showed that more than 75 per cent of the seropositive population did not know that they had contracted coronavirus in the past. This suggests seroconversion, that is antibody formation has happened even with silent infections," the release quoted R Hemalatha, Director, NIN, as saying.
According to the study, individuals who had displayed prominent COVID-19 symptoms as well as those who were asymptomatic, both had equivalent seroprevalence of around 54 per cent. Eighteen (18) per cent of the study group had been tested earlier and found to be positive for the coronavirus.
Ninety per cent of them were found to be seropositive, suggesting that they retain the antibody response. "This study brings a comprehensive perspective of potentially protective immune response against the coronavirus in the city’s population.
The data indicates that the population of Hyderabad might be slowly moving towards herd immunity, which will be certainly accelerated by the ongoing vaccination effort," said Rakesh Mishra, Director, CCMB.