At least 72 per cent of healthcare workers and 54 per cent of the general population in five Bengal districts have developed antibodies against Covid-19, a recent serosurvey report, prepared by the Centre’s Indian Council of Medical Research (ICMR), has said.

The serosurvey is a test of blood serum from a group of individuals to determine seroprevalence or the presence of antibodies against a virus.

Sources in the Bengal state health department said that in June this year, the ICMR, with the help of the state health department, conducted the survey in five Bengal districts — Alipurduar, Bankura, Jhargram, South 24-Parganas and East Midnapore — in order to know how people in those areas had developed antibodies ahead of the third wave.

The survey was conducted among around 400 people from the general population and 100 healthcare workers, including doctors, in each district at random.

The report was issued by the ICMR late last month.

According to the report, Alipurduar reported 88 per cent positivity of Covid-19 antibodies among the healthcare workers, highest among the five districts. This positivity among healthcare workers is the lowest in Jhargram, at 72.7 per cent.

The other three districts, Bankura, South 24-Parganas and East Midnapore, reported 79, 82.7 and 78 per cent, respectively, of antibodies among healthcare workers.

In the general population, 66.7 per cent of people from Bankura were found positive with Covid-19 antibodies, while East Midnapore reported the lowest positivity, at 53.9 per cent.

Alipurduar, Jhargram and South 24-Parganas reported antibodies in 59.1, 54.1 and 62.2 per cent of the people tested.

Senior health officials said that after the pandemic hit the country, the ICMR had started conducting such surveys to know about the presence of antibodies against Covid-19 in a bid to plan further health measures.

“The serosurvey is a method to guide us about public health response to the pandemic,” said a senior health department official.

“This is the fourth time that the government is conducting such a survey since the Covid-19 pandemic spread in our country. The ICMR did not claim openly that those who had reported antibodies against the virus have grown herd immunity, but in effect it reflects the same. However, we need to examine whether the antibodies are adequately protective or not,” the official added.

A section of health officials claimed that they found such a survey report “a major positive”.

It has been found that those having antibodies of the virus rarely reported serious suffering because of the pandemic, they said.

“If you look at the data, you can assess that doctors and healthcare workers have antibodies in high numbers. This happened because the healthcare workers have had to handle Covid-19 patients directly. We consider this a report of hope,” said Shyamal Soren, the chief medical officer in Bankura.

However, other health officials were more wary.

Many said that the time to declare herd immunity was yet to arrive.

“Those with antibodies may be competent to combat a specific strain of the virus. But the coronavirus has been mutating regularly and so we can’t say for sure that the antibodies present in people right now would act as a protective shield against all strains, and that those with antibodies already have herd immunity,” said a senior health official in Birbhum.

The Indian Council of Medical Research, the apex body in the country to formulate, coordinate and promote biomedical research, was founded in 1911 and is headquartered in New Delhi.