In a heartening development for health authorities, a surveyconducted in Mumbai has indicated that slum dwellers and women are at theforefront in the march to herd immunity against the coronavirus.
The 'Serological Surveillance for SARS-CoV2 Infection'survey was done by BrihanMumbai Municipal Corporation, along with NITI Aayogand TISS for 12-14 days in the first half of July covering 6,936 people.
Conducted in 3 selected BMC wards, those surveyed comprised61 per cent poor slum dwellers and the rest living in buildings or middle-classhousing complexes.
The survey threw up some unexpected and startling results,showing that 57 per cent of those tested in the slums were exposed to anddeveloped antibodies against the SARS-CoV-2 Virus, compared to merely 16 percent in housing complexes.
In the surveyed locations of Matunga, Sion, Wadala(F/North), Chembur and Tilak Nagar (M/West) and Dahisar and Mandapeshwar(R/North), it was also revealed that more women had developed antibodiescompared to men.
For the slums, the figures showed 59.30 per cent women (outof 2,297 tested) and 53.20 per cent men (out of 1,937 tested) had developedantibodies against Covid-19.
In the housing complexes, 16.80 per cent of women tested and14.90 per cent of men tested had developed antibodies.
Overall, around 40.50 per cent of the people surveyed inMatunga, Chembur and Dahisar areas were exposed to Covid-19, with Matunga -adjacent to Dharavi slum - having the highest exposure rate of 57.80 per cent.
The BMC interprets this high exposure in slums to sharedcommon facilities like toilets, water-taps, high population density and lack ofphysical distancing compared to the residents in housing complexes.
With the results suggesting more asymptomatic infections,this higher exposure in slums points to an extremely low death rate in Mumbai -"as low as 0.05 to 0.10 per cent" - instead of the existing 5.5 percent.
"So, despite the high exposure to Covid-19 in slums,the survey results indicate that the fatalities are not that high though therecould be many factors behind this," explained a civic official.
The BMC top brass is also startled since none of the peoplesurveyed had taken RT-PCR tests for Covid-19, implying they wereasymptomatically infected, and the numbers of such asymptomatic persons ishigher than expectations.
The official explained that the presence of antibodiesindicated that a person had been infected, fought off the virus and in theprocess developed a certain level of resistance to the virus.
The presence of more people with antibodies in a communityis considered a positive sign as the virus then has limited scope to spread,implying that measures like wearing masks, and physical distancing weresuccessful in these areas.
At the same time, even the lower presence of antibodies inthe housing complexes is considered encouraging as it points to lesser numberof infected people, due to better hygiene, more physical distancing and otherinterventions by the BMC, the official added.
"These results will be valuable to learn more aboutherd immunity. Although it is still unclear what level of prevalence leads toherd immunity, findings indicate that, at least in slums, this could beattained sooner than later, if the immunity exists and persists in asignificant proportion of the population," the BMC said in a statement.
The anti-SARS-CoV2-IgG antibodies were detected usingChemiluminescence assay (CLIA) by Abbott group, in what is billed as thelargest such cross-sectional survey in India.
It was carried out in collaboration with Kasturba MolecularDiagnostic Laboratory, Translational Health Science and Technology Institute,ATE Chandra Foundation and IDFC Institute.
The development comes a fortnight after the World HealthOrganization (WHO) acknowledged the success of the Maharashtra government incombating the Covid-19 outbreak in Dharavi.