A third of Delhi’s population exposed to COVID-19, according to latest sero survey

The second serosurveillance conducted in Delhi has found about a third of its population has been exposed to the COVID-19 infection, according to the state's health minister Satyender Jain.

The practice of serosurveillance began in the national capital last month and is going to be a monthly affair, conducted in several parts of the country. The survey conducted in Delhi is being carried out by Delhi Government and the National Centre for Disease Control (NCDC).

About 29.1% of the population of the city has been exposed to the infectious SARS-CoV-2 virus, which is an increase in overall numbers from the previous month's sero survey. In July, the first serosurveillance conducted in the capital found about 23% people to have had antibodies for the new coronavirus infection.

The increase in the number of people who have been exposed to the virus means more people have developed antibodies against the infection, which amounts to roughly about 58 lakh people in the city with a population of about 2 crore.

The second sero survey in the city was carried out between 1 and 7 August 2020, and included samples from 15,000 individuals from different parts of the city. The overall positivity rate in the city has also dropped significantly, from 30% to about 7%.

According to the state's health minister, herd immunity in the population could be achieved "when up to 40% of the population has antibodies specific to the virus".

Not even close to herd immunity: WHO

Not even close to herd immunity: WHO

According to some recent study-based reports, in some of the most densely populated areas of the world, there is a possibility of herd immunity being achieved or at least being close to it. These areas include New York City in the United States as well as Mumbai, the capital of the Indian state of Maharashtra, where a recent sero survey revealed that 40% of the people had been diagnosed with COVID-19.

It is believed that 70% of the population must be immune to the virus to produce herd immunity against an infectious disease. At the same time, many international medical experts and scientists have said that even if 50% of the population has antibodies against the virus, it can help in preventing the spread of the disease.

Read more: What is herd immunity

The World Health Organization (WHO), however, has stated that the world is not even around developing herd immunity against COVID-19. The WHO's statement comes as the death toll rose to more than 7.8 lakh deaths worldwide from COVID-19.

According to WHO's head of emergency affairs Dr Michael Ryan, "As a global population, we are not even close to the immunity level necessary to prevent the spread of the disease. This is not a solution, nor is there a solution that we should wait for."

At the same time, Dr Bruce Alward, a senior advisor to the WHO chief, said that a large-scale immunisation programme could cover a population of more than 50% in an effort to achieve herd immunity.