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Importance, Results & Impact of Mumbai’s Sero Survey

This blog describes How the Serological Survey Conducted amongst Slums & Non Slums in a densely populated city like Mumbai will help to understand our immunity level against COVID-19

Why is Sero-prevalence Study Conducted?

Seroprevalence study is conducted to analyze the impact of a disease, its mortality and herd immunity based on gender differences by conducting a serology test – the diagnostic test that identifies how a type of person produces antibodies and antigens against an illness like coronavirus disease. This shows how immune their system is against the virus.

While antibody test for COVID-19 depicts the number of people that were exposed to coronavirus earlier but were asymptomatic to the disease, antigen test for COVID-19 indicates how many of them are currently active cases. Learning about both these numbers considering asymptomatic & symptomatic count helps researchers derive the criticality of the virus in a type of individual. Thus, helping them understand a person’s immunity against the virus. These results become extremely important for health experts and the government to learn, understand and tackle the situation for the given population.

In July, BMC officials initiated a sero survey, first of its kind in 3 wards of Mumbai (Matunga (FN ward), Chembur (MW ward) and Dahisar (RN ward)) screening over 8,000 residents of Central Mumbai, targeting slum (high density of population) & non-slum (low density of population) both. This was the largest survey study for Dharavi residents, conducted by BMC, TIFR & NITI Aayog. LiveHealth & Thyrocare contributed as the operational partner in the survey to digitize the entire screening workflow for the survey.

It is also being conducted in different parts of India like Bengaluru, Delhi, etc. as a necessary step to screen SARS CoV-2 in order to study the rate of spread and the likelihood to control/contain the virus within the population.

How was the study done?

For 18 consecutive days, over 40+ phlebotomists accompanied by BMC officials went door to door to collect samples and capture household survey details, on the mobile app (powered by LiveHealth). The technology enabled phlebotomists to digitally capture household details and take samples on pre-barcoded tubes by Thyrocare; scaling the rate of entire operation. Batches of samples for high population density areas, i.e. slums & low population density areas (i.e. non-slums) were created separately to specifically study herd immunity in each of them.

Collected samples were taken to the Kasturba (Nair) Hospital, Mumbai to test COVID-19 antibodies. The centre utilized LiveHealth Lab Automation Software Interfaces to process samples everyday. The automated testing facility enabled error-free testing of more than 500 samples daily. Soon after testing, printed reports were circulated to slums & digital reports were emailed to non-slums participants.

Utilizing digitization right from capturing survey questionnaires to sample collection with barcodes, automated testing to report delivery; highly maintained the quality and accuracy of information throughout the process. Despite the geographical distance between each centre and lockdown limitations, the dedicated contributors & latest tech support enabled faster testing with error-free reports at scale.

Results & Impact

The finding derived the rate at which COVID-19 is spreading amongst the population of Mumbai, India.

Sero-survey dataAntibody study (men v women)

  • Out of 6936 people tested – 61% were slum & 39% were from the non-slum/residential areas
  • 57% of the slum population & 16% of the residential population (non-slum) were exposed to & developed antibodies against COVID-19 disease.
  • Women generate a higher amount of antibodies as compared to men in both slum & non-slum areas.
  • Among people in slums, 59.3% of women tested, and 53.2% of the men tested had antibodies against SARS nCOV.
  • In non-slum areas, 16.8% of women tested and 14.9% of men tested had developed antibodies.
  • *Infection Fatality rate is 0.05 – 0.1% as compared to **Case Fatality rate which is 5-6%

*Infection Fatality rate is the ratio of No. of non survival tested positive (COVID-19 infected) to the Total No. of Tested Positive (COVID-19 Infected)

**Case Fatality rate is the ratio of the No. of non survival suspected to have COVID-19 to the total No. of suspected COVID-19 case

The next course of the survey is to begin in the 2nd week of August, targeting the same wards to study if any change persists in the antibody development after 3 weeks of round 1.

Based on this study, researchers will utilize the data & the government will plan the next course of action to contain and manage the pandemic, while continuing to revive the country.

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