The slums in India's financial capital are showing signs of herd immunity but it is too soon to conclude

• Urban cities in the country including Mumbai, Delhi and Ahmedabad are showing a dip in the number of infections and cases.
  
• BMC Sero survey indicates that 57% from slums in three wards in Mumbai have developed antibodies
  
• Experts now believe that some parts of the country, especially the slums of India’s financial capital have developed Herd Immunity.
  
• Herd Immunity occurs when a large number of people become immune to a contagious disease after being infected to it.
  
• Business Insider India spoke to experts to understand the road ahead from here.

Herd immunity occurs when a large number of people become immune to a contagious disease after being infected to it. The latest sets of data from the two of India’s biggest metro cities, New Delhi and Mumbai, has sparked the hope for herd immunity against COVID-19 but experts warn it may be too soon to rejoice.

More than half of the population residing in slums in three different regions in Mumbai contracted coronavirus and developed its anti-bodies, according to a sero-surveillance study conducted by the city’s civic body, Tata Institute of Fundamental Research (TIFRE) and NITI Aayog (India’s premier think tank).

Mumbai, where 800,000 people live in slums, has reported over 110,000 infections and 6,000 fatalities till June 29. The sero-surveillance started on June 3 and 6,936 samples out of an estimated 8,870 were collected from slum and non-slum population of three civic wards - R-North, M-West and F-North - in the first half of July.

The case for possible herd immunity

“Although it is still unclear what level of prevalence leads to herd immunity, findings indicate at least in slums this could be attained sooner or later if the immunity exists and persists in a significant proportion of the population." the BMC statement read.

“If someone is exposed and they develop antibodies, we can detect those antibodies and it gives us a relatively decent indicator that they were exposed. The interesting thing about the study is it was only looking for asymptomatic individuals. Symptomatic people are going to the system, they are getting treated, managed etc. Asymptomatic is something none of us could understand,” Dr. Marcus Ranney, General Manager (India) Thrive Global explained.

This comes a week after a Delhi government survey stated that 30% of the people living in the national capital had anti-bodies of COVID-19. However, the jury is still out on whether herd immunity can stave off COVID-19 infections in the future.

Here’s why herd immunity can’t be taken for granted

“We have to be very careful with the concept of allowing people to get infected with this virus to develop natural (herd) immunity. This approach does not seem to work (in this case). This is a very contagious infection, and it is clear that the virus can be devastating to those over the age of 60 or with underlying medical conditions,” said Issac Bogoch from the University of Toronto, Canada said in an interview with IANS.

The other downside of living in the hope of herd immunity is that it could put a lot of vulnerable people at risk.

“Asymptomatic carry the same viral load as a symptomatic patient and they are not protected. An asymptomatic carrier is as lethal and as vulnerable as symptomatic. One asymptomatic can spread it to 217 people if the person is in a closed/family range, ” Prof. Dr. Sanjeev Bagai, the chairperson of Nephron Clinics, told Business Insider India

Many of these people who get the virus passed on to them could be older people and those with co-morbidities like diabetes, Hepatitis and heart diseases to name a few.

India has been the third-worst affected country and has reported 1.5 million cases. And even if a person does develop antibodies to fight COVID-19, they may not stay in the body forever. Research studies across the world have shown that the immunity drops 8 weeks or so after contracting COVID-19, according to Bagai.

Even Ranney, who hopes that there will be herd immunity someday, warns against lowering the guard too soon.

“We do not know the period of time this immunity lasts. We could see a repeated infection in the same individual (recovered patients). A King’s College study in London was suggestive that the immunity drops quite significantly,” Dr. Ranney said.


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