Mumbai may develop herd immunity by December-January: TIFR report

MUMBAI: A mathematical projection on the ongoing Covid-19

pandemic

worked out by

the Tata Institute of Fundamental Research

(TIFR) and submitted to the

BMC

has said that by December this year or January next year, almost 75% of the people living in

slum pockets

in the city and in 50% of the non-slum pockets would have antibodies.

However, the model hasn’t accounted for the threat of reinfection, which has emerged as a concern across the world in the past fortnight.

The TIFR team has said the city should open up by 30% in September in terms of attendance in offices and capacity of transport systems. This could be increased to 50% in October. “The city should be further opened up gradually and become fully operational by around November 1,” said Dr Juneja. However, social distancing norms should be observed in public transport and

hygiene measures

should be followed such as mandatory use of masks, hand-hygiene and regular disinfection of surfaces in trains and workplaces.

Given the sharp economic decline, there has been a demand to open up Mumbai (as well as the rest of the country) soon. The TIFR team hence studied various scenarios and found the November 1 date would lead to least amount of hospitalisations and deaths.

Opening up mid-September, they said, could lead to a second wave of hospitalisations and rise in critical cases in Mumbai, which hit a plateau as far as Covid cases go in the May-June period.

Incidentally, the city recorded higher-than-usual number of cases (1,737) on Saturday, mainly as a fallout of the increased outings during the recently-concluded tenday Ganpati festival. As per BMC’s update, Mumbai’s overall tally now is 1,53,712, with 7,832 deaths.

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

Dr Juneja said the projected hospitalisations increase from around 3,000 a day to a peak of about 4,200 a day with the September 16 opening, while the increase would be from about 1,600 a day to around 2,100 a day with the November 1 opening. “Our conclusion, based on our simulations, is that the impact of fully opening up the economy on November 1 is easily manageable with the current medical infrastructure. Schools and colleges opening in January do not lead to excessive increase in infections,” the report said.

The TIFR team partnered with the BMC to conduct the three-ward sero-surveys in Mumbai. The first such survey in July indicated that 57% of the slums and 16% of the non-slum pockets had developed antibodies. The TIFR analysis of the second serosurvey is likely later this month.

The TIFR simulations suggest that by around December 2020 and January 2021, the prevalence (fraction of the population infected) can be seen to be stabilising close to 75% in slums and 50% in non-slums. “This stabilisation and high prevalence indicates 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.

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