Signs Of Covid-19 ‘Herd Immunity’ Seen in Small Population Groups In Pune: Report

Despite findings of the latest serological survey, researchers are still not suggesting that Pune city is approaching ‘herd immunity’ against Covid-19.

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A new study revealed that close to 85 percent of people in Pune who were found infected with the deadly coronavirus in an earlier serosurvey have developed protective antibodies.

As reported by The Indian Express, earlier this year in July and August the serosurvey conducted in Pune, had found that about 51 percent of the people had been infected with the virus

The latest finding is the result of a follow-up study conducted in five areas- comprising three or four municipal wards each of the city.

What are serosurveys?

It is the collection and testing of serum (or proxy such as an oral fluid) specimens from a sample of a defined population over a specified period of time to estimate the prevalence of antibodies against a given specific infectious pathogen as an indicator of immunity.

The serosurveys which were conducted in several Indian studies estimated the prevalence of the disease by testing for antibodies among surveyed population groups.

However, the presence of antibodies does not necessarily mean that the person has also acquired immunity it just indicates that the surveyed person has been infected with the disease at some point in time.

Immunity comes only if the infected person develops what is called ‘neutralizing’ or ‘protective’ antibodies, a small subset of antibodies.

Signs of Covid-19 Herd Immunity Seen in Small Pune Population

Serosurveys estimate the wider prevalence rate, because not every infected person shows symptoms and gets tested. Reportedly, this follow-up study conducted in Pune on an earlier serosurvey to detect the presence of ‘neutralizing’ antibodies in infected persons is the first of its kind.

Even though researchers have been conscious of not calling this ‘herd immunity’, it has become the first documented case in the country where a large population has been infected and the rate had gone up so high that the concept of herd immunity could already be playing out.

The findings in the study were supported by the fact that in Lohianagar, the prabhag with the highest disease prevalence, indicated that the incidence rate has fallen sharply in the last three months, which means that there may be population-level protection against the disease.

Dr. Gagandeep Kang, one of the co-authors of the study told The Indian Express, “I don’t think we can still say that Pune has achieved, or is reaching, herd immunity. But the study is important because it shows that wherever there was high seropositivity, the incidence rate has fallen subsequently.”

So far, Pune district’s overall infection count went up to 3,33,726 with 859 new cases on Thursday. With 12 deaths reported during the day, the district’s death toll rose to 8,231, the health department said.

The Directorate of Health Services had last week warned that the second wave of the pandemic is likely in January- February and asked officials concerned to ramp up testing in the state. While residents have been guided to protect themselves.

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