Senior citizens in slums were most exposed to SARS-CoV-2 among all age groups, while senior citizens in non-slums were least exposed to the virus, according to Mumbai’s sero survey findings.
In slums, 62.6 per cent senior citizens had been exposed and developed antibodies against Covid-19, as opposed to 12.6 per cent in residential buildings.
Of the 4,234 slum-dwellers who were surveyed, 56.1 per cent between 12-24 years, 52.9 per cent between 25-40 years, 59.6 per cent between 41-60 years, and 62.6 per cent aged above 60 had developed antibodies.
In non-slums where 2,702 people were tested, the trend reversed. In the 12-24 year bracket, 18.8 per cent had developed antibodies, decreasing to 15.8 per cent in the 25-40 age group, 15.9 per cent in the 41-60 age group, and to a mere 12.6 per cent in the 60 year plus group surveyed.
“The government’s advisory asked senior citizens to stay at home. This finding iterates that in non-slums, educated and well-aware people took maximum precaution in that age group and were least exposed,” said Dr Pradeep Vyas, state health secretary. He added that in slums, senior citizens had no option of preventing physical distancing due to shared toilets and were most vulnerable to the infection. “It is also a matter of joy that in slums we have reached this level of immunity,” he added.
Scientists were more circumspect. Dr Jayanthi Shastri, head of microbiology in Nair hospital, said, “This could also be a coincidental finding. There may be no co-relation with age,” she said.
Professor Sandeep Juneja, Dean of School of Technology and Computer Science in Tata Institute of Fundamental Research (TIFR), who was part of the team that conducted the survey, also said at this point “it is hard to draw conclusions”.
Dr Daksha Shah, deputy executive health officer, BMC, said these are findings that will have to be analysed when a second sero survey is conducted.
The sero survey, conducted in July first two weeks jointly by BMC, TIFR, and Niti Aayog, found sero prevalence in slums 3.5 times higher than in non-slums.
In Matunga (F North) where 3,327 samples were collected, 57.8 per cent people in slum were exposed and had developed antibodies, as opposed to 17.4 in non-slum pockets. In Chembur (M-West) 2,460 samples were taken, slums had seroprevalence of 56.7 per cent and non-slums 15.6 per cent. Dahisar (R-North), where 1,149 samples were collected, has seroprevalence of 51 per cent in slums and 11.4 per cent in non-slums, the lowest amongst all three wards.
The survey found that infection fatality rate was lower in slums than non slums, although the exposure was much higher in slums.
Women living in both, slums and residential buildings, seemed to have been more exposed to Covid-19 and developed faster immunity than men. In slums, 59.3 per cent of women tested had developed antibodies as opposed to 53.2 per cent men. In residential buildings, 16.8 per cent of total women tested had developed antibodies, and only 14.9 per cent men.
A second sero survey, starting August 10, will study in greater detail what role gender plays in Covid-19 infection and mortality.
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