13 June, 2021

Known Unknowns

To achieve herd immunity in a 1.38 billion population, we need to cover 828 million people! The truth is: it may take years, and we still won’t be sure.

Known Unknowns

In conversations with family and friends these days, I am most frequently asked about COVID-19 vacci­nes. My inability to give definitive answers has ­disappointed many who get their Covid information from social media and forwarded messages. The WHO lists over 200 candidate vaccines for Covid being pursued ­seriously, including 49 being clinically tested on human ­volunteers and 11 that have moved to Phase 3 trials to test their efficacy after being shown to be safe. Considering that it takes 10-20 years to produce a successful vaccine, this speed is phenomenal, and made possible by science, new ways of testing and financing vaccines. But bottlenecks remain.

India supplies about 40 per cent of the world’s vaccines—about 2.3 billion doses, of which 74 per cent are exported and 26 per cent consumed domestically. To achieve 60 per cent coverage for 1.38 billion people—often cited as the herd immunity threshold—India would have to vaccinate 828 million people. Since all leading vaccine candidates would be needed in at least two doses,...

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