Mumbai's slums may be reaching herd immunity, study finds

Some of the largest slums in Mumbai, India, may be nearing herd coronavirus immunity, a new serological survey found, Bloomberg reports.

The study tested 6,936 people across three suburbs in Mumbai — Dahisar, Chembur, and Matunga — and discovered that 57 percent of the subjects had coronavirus antibodies, a figure far higher than the 21 percent found in New York City in April and 14 percent in Stockholm, Sweden, in May. Per Bloomberg, epidemiologists generally believe a population must reach infection levels of 60 percent to achieve herd immunity, so the study indicates the neighborhoods are pretty much there. The survey appears to go hand-in-hand with a steep decline in cases in the slums in recent weeks, despite India having the world's fastest growth in infections overall.

Social distancing is a challenge in the crowded Mumbai neighborhoods, which seemingly makes them well-suited for the virus' spread, and the study suggests that it did so widely. Fortunately, the population in the slums is young and more likely to avoid severe cases of COVID-19. That, coupled with successful government containment measures that helped catch cases early and ensure high quality care, have kept the fatality low in the slums, even if many infections went undetected, Bloomberg notes.

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It's encouraging that some of Mumbai's slums may be closing in on herd immunity without experiencing a high death rate, but the jury is still out on how long immunity lasts. It's also worth noting antibody rates were not nearly as high in other parts of Mumbai, where social distancing is more feasible. Read more at Bloomberg.