Results of the latest sero survey indicate that Delhi is closer to attaining herd immunity against the coronavirus, News18 reported on Tuesday. Experts say that herd immunity is achieved when the majority of a population becomes immune to a disease through vaccinations or through mass spread of the infection.

The fifth sero survey indicates that every second person in the national Capital has developed antibodies against the coronavirus. This implies that about one crore people have already contracted Covid-19 and recovered from it.

This sero survey began on January 11 and authorities collected more than 28,000 samples during the exercise. “In one district, the prevalence is around 58%, which clearly shows that a large number of people have developed antibodies against the virus,” a senior government official told The Indian Express.

Dr Shobha Broor, the former head of microbiology at All India Institute of Medical Sciences, said the survey revealed that there have been many asymptomatic infections in the city. “The number may go up to 70% in the next round as more people would have got vaccinated by that time,” she said. “Having [the] presence of antibodies will not affect the ongoing vaccination drive in any case. Those who have developed antibodies can go ahead and take the shot as the vaccine will further boost the response.”

Dr Neeraj Nischal, associate professor at the department of medicine at AIIMS, said the high prevalence of antibodies can help in tackling the pandemic. “It shows that a lot of asymptomatic infections did happen in the course of the pandemic, which were not reported at that time,” he said. “This is our natural way of acquiring herd immunity as approximately 50% have developed antibodies against the virus.”

The first sero survey in Delhi was conducted in July. It showed that 23.48% of Delhi’s population had developed antibodies against Covid-19. The second survey, conducted in August, revealed a prevalence of 29.1%. Over 25.1% of Delhi’s population had antibodies, showed the third sero survey done in September. The fourth sero survey conducted in October showed that 25.5% of the population had developed antibodies.

According to the US’ Centers for Disease Control and Prevention, serology tests are “those that look for antibodies in blood”. “If antibodies are found, that means there has been a previous infection.” However, the CDC adds that:

“A positive test result shows you may have antibodies from an infection with the virus that causes COVID-19. However, there is a chance a positive result means that you have antibodies from an infection with a virus from the same family of viruses (called coronaviruses), such as the one that causes the common cold.”


Meanwhile, India is also conducting a mass coronavirus vaccination drive. India has so far vaccinated 20,23,809 people against Covid-19, according to Union Health Ministry data.

The Centre is planning to inoculate 30 crore people over the next few months. About 3 crore healthcare and frontline workers are being vaccinated first. After that, people over the age of 50 and those with comorbidities would get inoculated.

India reported 9,102 new coronavirus cases on Tuesday, taking the overall count to 1,06,76,838. The country’s toll rose by 117 to 1,53,587. The number of active cases stood at 1,77,266, while the recoveries reached 1,03,45,985.