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Person using a pulse oximeter in Bengaluru, Karnataka, India. Photo by Syed Ali.

Recently, a discussion moderated by Richard Cash, Senior Lecturer on Global Health at Harvard T.H. Chan School of Public Health, brought together Satchit Balsari, Assistant Professor of Emergency Medicine at Harvard Medical School, and Manoj Mohanan, Associate Professor of Public Policy, Economics, and Global Health at Duke University, to discuss “A Class Apart: COVID-19 Seroprevalence in India.” Together, they explored the findings and implications of a recent seroprevalence survey (the number of individuals in a population who test positive for a specific disease based on serology specimens) conducted by Professor Mohanan’s team in India.

Professor Balsari began by recalling the initial state and societal response to the pandemic in India. Despite the inadequacies of the public health infrastructure and the failures in healthcare delivery, the case fatality ratio in India remains among the lowest in the world. In this context, Balsari presented a set of questions about the Indian response that have been posed by experts. Some attribute the low fatality rate to India’s “protective demographics” — the fact that the majority of Indians alive today are in their twenties. Others would maintain that it is precisely because these absolute numbers are so low that the Indian state response to the pandemic need not have mimicked the European response.

Some would argue that India’s middle-aged population, compared to their counterparts in the US or Europe, may have more untreated comorbidities (such as diabetes or hypertension) and respiratory diseases because of the air quality in India. Still others would argue that we simply do not know if any of this is true because the data necessary to either defend or refute these claims is simply not available.

Professor Mohanan, whose recent study was funded by ACT Grants (India) and carried out by IDFC Institute, joined the conversation to discuss the results. As per the findings of the study, it is estimated that a large portion of the population in the locations surveyed have antibodies and have therefore been exposed to the virus. From studies conducted in Mumbai, it was discovered that by the end of July, 58 percent of the population in Mumbai’s slums had already started showing the antibodies. The number was lower in the non-slum population, at 17 percent. His findings further suggest that 44.1% of the population in rural areas and 53.8% in urban areas in the region of Karnataka tested positive for antibodies to COVID-19.

According to Professor Mohanan, a second round of seroprevalence survey among the same population could produce lower numbers for several reasons — and the deviation could be due to the change in the sample. Another reason could be the decline in antibodies over time, which is normal, considering that once the infection passes, the body has no reason to continue producing antibodies.

The seroprevalence studies were conducted in Mumbai, Karnataka, and among returning migrants from Bihar. “Each of these studies revealed significantly higher prevalence than was anticipated at this stage; the findings have ramifications on response analysis, but also on current containment strategies, on medical response, on reopening of the economy, and discussions about herd immunity,” noted Professor Balsari.