New Delhi, June 25 -- In the spring of 2021, as India's second COVID-19 wave overwhelmed hospitals from Delhi to Chennai, a quietly dangerous idea was still circulating in the public conversation: that South Asian populations possessed some natural advantage against the coronavirus. Politicians had floated it. Wellness influencers had promoted it. A handful of early projections, built on incomplete data, had seemed to support it. The virus, those voices suggested, would not strike here the way it had struck elsewhere. It did.

The South Asian immunity myth was not a fringe belief. It was repeated often enough that it sometimes substituted for analysis - and, in some cases, for precaution. Understanding how it spread, why it was wrong, and...