Studies that tested for SARS-CoV-2 antibodies — an indicator of past infection — in December and January estimated that more than 50% of the population in some areas of India’s large cities had already been exposed to the virus, which should have conferred some immunity, says Manoj Murhekar, an epidemiologist at the National Institute of Epidemiology in Chennai, who led the work. The studies also suggested that, nationally, some 271 million people had been infected
1 — about one-fifth of India’s population of 1.4 billion.
These figures made some researchers optimistic that the next stage of the pandemic would be less severe, says Ramanan Laxminarayan, an epidemiologist in Princeton University, New Jersey, who is based in New Delhi. But the latest eruption of COVID-19 is forcing them to rethink.
One explanation might be that the first wave primarily hit the urban poor. Antibody studies might not have been representative of the entire population and potentially overestimated exposure in other groups, he says.