90%+ in Delhi have Covid antibodies: 6th sero study

Published on Oct 28, 2021 06:42 AM IST

Samples from 28,000 people were tested to see if they had antibodies to the virus, which causes Covid-19, and over 90% of them turned up positive

A health worker collects samples during the previous sero survey in the Capital. (Sanchit Khanna/HT PHOTO)
A health worker collects samples during the previous sero survey in the Capital. (Sanchit Khanna/HT PHOTO)
By, New Delhi

More than 90% of Delhi’s population likely has some form of protection from Sars-Cov-2, the preliminary findings of the latest serological survey in the Capital suggest.

Samples from 28,000 people were tested to see if they had antibodies to the virus, which causes Covid-19, and over 90% of them turned up positive, an official aware of the matter said, citing the study’s report submitted to the government.

“A high sero-prevalence is good news, this means a good chunk of the population will be protected from the infection,” the official said, asking not to be named.

It was not immediately clear how many of these people had antibodies as a result of an infection or vaccination. But the survey, a Delhi government health official told HT last week, covered these details.

According to the first official quoted above, the preliminary report includes details such as district-wise, age-wise, and gender-wise sero-prevalence and a more detailed report is likely to be submitted around Diwali, which will be celebrated on November 4.

The current round, the sixth such study in the Capital, was the first full sero study after the devastating April-May wave of infections. The last survey, for which samples were taken in April, showed an antibody prevalence rate of 56%.

For the latest round, the sampling was done in September and the officials determined vaccination status as part of the process.

A portion of the samples collected will also be analysed for level of antibodies, which could help researchers estimate how protected the population could be. These test results are awaited from the laboratory at the Institute of Liver and Biliary Sciences (ILBS).

“This round of the survey was conducted in great detail, so it will take some time to analyse the data. A more detailed report is likely to be submitted in early November, around Diwali,” the second official quoted above said last week.

These numbers could explain why Delhi’s cases have remained low despite the city having lifted most curbs on activities. The average weekly positivity rate of samples has remained under 0.10% since late July.

Experts have previously warned against focussing on concepts of herd immunity and population immunity — the principle that says if enough of the public is protected, there will be a wall of protection from the virus.

The Sars-Cov-2 virus has mutated on multiple occasions to make past protection redundant to some extent and become so transmissible that it raised the threshold for such protection.

The previous five surveys returned readings of 56.13%, 25.5%, 25.1%, 29.1%, and 22.6% respectively.

The current findings strengthen what was earlier found in a study from the All India Institute of Medical Sciences (AIIMS) that collected data at the peak of the second wave showed a seropositivity of 67% in Delhi.

Further, a sero survey among staff members in the Council of Science and Industrial Research in Delhi showed a seroprevalence of 80% after the second wave.

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  • ABOUT THE AUTHOR

    Anonna Dutt is a health reporter at Hindustan Times. She reports on Delhi government’s health policies, hospitals in Delhi, and health-related feature stories.

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