In some good news amidst the Covid-19 crisis that the country has been facing since last year, top research institutes like CCMB and NIN based in Hyderabad have announced that the country is nearing herd immunity. Some of the recent studies too show a similar trend.
A joint effort by CSIR-Centre for Cellular and Molecular Biology (CCMB), ICMR-National Institute of Nutrition (NIN) and Bharat Biotech has estimated the seroprevalence of antibodies against coronavirus SARS-CoV-2 in Hyderabad. The study of around 9,000 samples has found that around 54% of Hyderabadis show antibodies against SARS-CoV-2, indicating prior exposure to coronavirus.
Scientists checked for antibodies against the virus in people across 30 wards of the city. At least 300 people, from each ward, all of them older than 10 years of age, were tested. Most of the wards showed a similarly uniform range of seroprevalence, from 50-60%. However, a few wards showed as much as 70% or as low as 30% as well.
Women showed a marginally higher seropositivity rate (56%) than the men (53%). Those above 70 years of age showed a lower seropositivity (49%), perhaps because of limited mobility and extra care taken by older individuals during the pandemic. Unsurprisingly, those who had Covid-19 positive cases in their own households, showed the maximum seropositivity of 78%. This was followed by those with known Covid-19 contacts outside their household (68%).
Dr A. Laxmaiah, Scientist ‘G’ at NIN, observed that having a larger number of rooms in houses and small family size households had low prevalence of coronavirus infection. “This multistage random sampling study on 9,000 people in the city of Hyderabad showed that more than 75% of the seropositive population did not know that they had contracted coronavirus infection in the past. This suggests seroconversion, that is antibody formation has happened even with silent infections,” said Dr R. Hemalatha, Director, NIN.
According to the study, individuals who had suffered prominent Covid-19 symptoms as well as those who were asymptomatic, both had equivalent seroprevalence of around 54%. At least 18% of the study group had been tested earlier and found positive for coronavirus. About 90% 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 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 Dr Rakesh Mishra, Director, CCMB.
He told The Sunday Guardian, “We are nearing herd immunity, but we should get vaccinated. We should come to a position where one crore vaccine doses per day should be administered. Herd immunity is possible through aggressive vaccination. Indian reinfection rate is the lowest in the world. Reinfected people are in single digits; 90% of the infected people developed antibodies.”
