Coronavirus: Has India achieved herd immunity?

According to a recent serological survey conducted by the Indian Council of Medical Research (ICMR), more than half of the residents in New Delhi have developed antibodies for the novel coronavirus. In other words, the survey revealed that half of the city's population has recovered after being infected with the virus since its outbreak in the South Asian nation in January 2020.

"New Delhi alone has registered more than 634,000 COVID-19 cases and over 10,000 deaths," M C Mishra, a former medical superintendent at the All India Institute of Medical Sciences, told DW.

"It is true that people have developed antibodies, but India is still far away from achieving herd immunity," Mishra said.

India, a country of 1.3 billion people, has registered the world's second-highest number of coronavirus infections, at about 11 million. Experts say the real number of infections in the country could be much higher than the official figure. Only the United States has recorded more COVID cases than India.

But, in recent weeks, new coronavirus cases and deaths have plummeted in the country, prompting many people here to believe the worst phase of the pandemic is finally over.

Can India feel relaxed?

Herd immunity is a phenomenon in which a significantly large number of people in a community develop biological resistance to a contagious disease — mostly after recovering from an infection — thereby curbing its spread across the population.

Does the recent sharp fall in COVID-19 cases in India mean the South Asian country has already achieved it or at least is close to achieving it?

Experts say the risk of another rise in cases cannot be underestimated. "In India, many people have been exposed to the virus, and that could possibly be the reason behind the falling numbers. But the situation is still dangerous," Samiran Panda, an epidemiologist, told DW. "The exact number of infections, or people with antibodies, is still unclear. We are still a long way from achieving herd immunity," Panda said.

V K Paul, the head of the India's national COVID task force, says the country needs a cautious approach in its battle against the virus. "A large population is still vulnerable. Vaccinations and following COVID-19 protocols are important," Paul told DW.

Arun Gupta of the Delhi Medical Council says that herd immunity should come from vaccination. "That really stops the spread of the disease and protect the rest of the population," Paul said.

COVID variants remain a problem

According to Health Ministry figures, the coronavirus had killed 154,918 people in India as of February 7. That's a mortality rate of 1.44%, much lower than that in the US and many European countries.

"The natural system handles the infections in a natural way, resulting in selection pressure on immunity genes. This may also explain a low COVID mortality rate in India," Rajender Singh, from the Central Drug Research Institute, told DW.

India reported its first coronavirus case on January 30, 2020, and its first death in mid-March. The daily cases peaked at more than 97,000 infections in September, with deaths averaging 1,000 a day that month. Since then, the number of deaths has been falling. India has recorded less than 84 coronavirus deaths in the last 24 hours. Two states — Maharashtra and Kerala — account for 70% of the total active cases in the country.

"We may be getting close to achieving herd immunity in some densely populated cities, but definitely not elsewhere yet," Shahid Jameel, a virologist in New Delhi, told DW, adding that the major issue right now is the emergence of virus variants.

"The UK went down to about 500 cases per day in summer and then the new infections rose to about 25,000 per day. So, it is not over yet," he added.

A recent study published in The Lancet magazine found that Brazil's Manaus city witnessed COVID resurgence despite a large number of people with antibodies. The possible reason behind the upsurge is believed to be a waning immunity from prior infections, and the spread of new, more infectious coronavirus variants.