New Delhi: After the latest serological survey suggested that 56.13% of the population have developed antibodies against coronavirus in January, medical experts said that herd immunity for Covid-19 is not clear and the number is variable.

In Delhi, Delhi health minister Satyendra Jain claimed that in the fifth serosurvey, which was the largest in the country so far, at least 56.13% of those covered had developed antibodies, and Delhi is slowly moving towards herd immunity. However, he also said that the experts have to take a call on it.

Meanwhile, in the nationwide serosurvey, it was found that one out of the five Indians may have been exposed to Covid-19 until now. The third nationwide serosurvey was conducted between 17 December 2020 to 8 January. The data also showed the seroprevalence figure of 21.5% among those surveyed. Dr Ravindra Mehta, a pulmonologist at Apollo Hospital, told The Sunday Guardian, “The herd immunity for the novel coronavirus infection is not clear. Experts say different numbers for attaining herd immunity. Some say it is 70%, while others say it is 80%. The numbers are variable.” He further told The Sunday Guardian, “If the virus is aggressive, then the immunity will go away as it happened in the United Kingdom. But if the virus is mild, in the lower number itself, herd immunity can be attained. In Delhi, herd immunity has been achieved because there is a lower number of cases, but after some days if it mutates, these numbers would mean nothing. So, we are yet to get to the conclusion.”

Mehta also told The Sunday Guardian, “Herd immunity is only there for a certain period of time. In the case of Covid-19, the immunity wanes in a month or so. So, if there is herd immunity now, it is not necessary it will be same after a month because the same immune people will become immune and the virus can spread quickly.”

Dr Jayalal, Indian Medical Association President, told The Sunday Guardian, “Extrapolating the data of serosurvey, we come to the conclusion that almost 70 million of the population in India have developed antibodies. This is a good number, but we cannot drop our guards. We have to follow social distancing norms and wear masks at public places.”

Talking about half of infection cases being reported from Kerala, the IMA president told The Sunday Guardian, “In Kerala, strict measures were followed in the initial stage of Covid-19. However, when the cases began to decline, people may have become careless and dropped their guard. This may have led to increase in cases in Kerala.”

According to the data, on Thursday, as many as 12,408 cases were reported in India of which 6,102 were from Kerala followed by Maharashtra (2,736).

Mehta further told The Sunday Guardian, “Herd immunity is a moving target and the number will not remain the same in the next month. Herd immunity in this month does not mean that the Covid has subsided in the country.”

Mehta also said: “With 50% antibodies in the recent serosurvey, we can say that there is a lower prevalence of the disease in the residents. However, this does not mean that Covid-19 has waned from the country.” Mehta further said, “The purpose of vaccination is to develop an immune response against the novel coronavirus infection in the population within a span of six to nine months.”