Delhi is moving towards herd immunity from Covid-18, with 50 to 60 per cent of people in one district having developed antibodies to the virus, as per the latest round of sero-survey, government sources said on Monday.
Herd immunity is what the authorities are trying to achieve with the vaccination programme, in which a critical mass of immune people can stop the spread of the virus by breaking the chain of transmission.
Delhi has a population of more than two crore, spread across 11 districts. The fifth and the largest sero-survey of Delhi was conducted in January 2021. In a sero-survey—conducted by the Delhi government in association with the National Centre for Disease Control—samples of blood are collected from the person’s body and then medical team tests whether antibodies have been formed against coronavirus in the blood or not.
Official figures from the health ministry say only 6.33 lakh people have been found infected in Delhi. But the survey indicates that the total figure could be more than 1 crore, sources said.
In one district, the number of the infected people was around 60 per cent. In the rest of the city’s 10 districts, the average is above 50 per cent—close to the magic figure required.
Herd immunity can occur in two ways—one by the natural spread of infection or by vaccination. As scientists and doctors, we always wish that herd immunity comes from vaccination.If antibodies against infection are found in 60 per cent of the population, then, in this case, we can assume that the rest of the population which does not have antibodies can also be protected from the infection.
The fifth sero-survey of Delhi is the largest sero-survey to date. A total of 28,000 people were sampled in this survey. Hundred samples were taken from every municipal ward of Delhi. The survey has been conducted from 10 January to 23 January.
The first sero-survey in the capital was conducted in June-July in which antibodies were found in 23.4 per cent people.