Coronavirus Mumbai update: Tata Institute expects 50% of city population to develop herd immunity by January

According to a report submitted to the Brihanmumbai Municipal Corporation (BMC), nearly 75 percent of people living in slum pockets in Mumbai and 50 percent of those residing in non-slum pockets would develop antibodies by December or January.

The study, published by the Tata Institute of Fundamental Research (TIFR), however, has not considered the threat of reinfection, which has emerged as a concern after the first confirmed case of reinfection in India was reported in Bengaluru.

A private hospital has reported that a 27-year-old woman from Bengaluru tested positive again nearly a month after she was treated and discharged from the hospital.

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The TIFR simulations suggest that by December 2020 and January 2021, the prevalence (fraction of the population infected) can be seen to be stabilising close to 75 percent in slums and 50 percent in non-slums, according to a Times of India report.

“This stabilisation and high prevalence indicate that Mumbai city may have more or less reached herd immunity by then and further new infections in the city will be substantially reduced,” the paper added.

Explainer: Reaching herd immunity in a viral pandemic

Herd immunity refers to a large portion of a community developing a degree of immunity to a virus, thereby reducing person-to-person spread. As a result, the whole community gains protection, not just those who are immune.

In the report, the TIFR team has said that Mumbai should open up by 30 percent in September in terms of attendance in offices and capacity of transport systems. This could be increased to 50 percent in October, the Times of India reported.

“The city should be further opened up gradually and become fully operational by around November 1,” said Dr Sandeep Juneja, Dean of School of Technology and Computer Science in TIFR.

"Our key observations are the second wave of hospitalisations and critical cases are much higher with the September 16th opening compared to the November 1 opening,” the report said.

On September 6 Mumbai saw the record spike of 1,910 new cases, taking its tally to 1,55,622. With 37 deaths, the toll in the city reached 7,869. The Mumbai Metropolitan Region (MMR), including Mumbai, added 5,407 new cases to its tally at 3,61,799. With 85 casualties, the cumulative toll mounted to 13,309 in the MMR.

India's COVID-19 tally of cases went past 42 lakh with a record 90,802 people being infected in a day.

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