Why have India’s Covid-19 cases plummeted?

Experts speculate that several factors are likely behind the decline in India’s case numbers, such as the country’s younger population or the possibility of rising immunity in urban areas.

Some experts warn that the low case numbers are more cause for caution than celebration — and that people can’t let their guard down, especially as new, potentially more contagious variants spread internationally.

Immunity in big cities

One factor behind the drop in cases could be a rise in people with antibodies, since there are “large numbers of people exposed to infection and thus protected,” said Shahid Jameel, a virologist and director of Ashoka University’s Trivedi School of Biosciences.

India has reported more than 11 million cases and 156,000 deaths since the pandemic started, according to a tally by Johns Hopkins University.

“This is a huge increase,” community medicine specialist Dr. Hemant Shewade said, adding that big cities may see “considerably reduced” transmission due to the rise in immunity.

However, India is nowhere near herd immunity. There may be enough population immunity to slow infections in large cities, but national herd immunity would require a vast majority of the country’s population to be immune either through previous infection or vaccination. India’s 11 million reported cases so far make up less than 1% of its 1.4 billion people.

“Herd immunity is not something we can consider for the entire country,” Jameel said. And antibody positivity rates vary widely across different regions — apart from the biggest cities, most other places in the country likely have much lower rates, he said.

Herd immunity remains unlikely even when adjusting for underreporting.

“The numbers of exposed people could be in the range of 150 (million) to 900 million — about 350 (million) to 400 million is a more reasonable estimate,” Jameel said, pointing to previous antibody surveys. But that estimate is still only about a quarter of the population. Even the most liberal estimate of 900 million is 65% of the population, which may not be enough to reach herd immunity.

And India might not achieve herd immunity for years, Adar Poonawalla, CEO of Serum Institute of India, the country’s largest vaccine manufacturer, has said.

“Until you get that real magical 90% herd immunity or vaccine immunity, which will come after three or four years, you really should exercise precautions,” Poonawalla said in a January interview with CNN.

Demography, geography and living conditions

India’s relatively young population may be another factor that has helped push down the country’s case numbers, since infections in younger patients tend to see milder symptoms and lower mortality rates.

“A younger population means largely asymptomatic infection or mild disease, which is not tested and does not show up in reported cases,” Jameel said.

Geography plays a part as well, Raman Gangakhedkar, former head scientist of epidemiology and communicable diseases at the ICMR, said.

“It’s also important to remember that around 70% of Indians live in rural areas, where you’ll find that ventilation is better and people’s bubbles are smaller,” he said. “A person living in a rural area doesn’t travel by bus or train, their network is smaller (…) There’s less risk compared to the risk for someone in an urban area.”

“We had a very long lockdown that was successfully followed, and we have been able to shift the curve by at least five to six months,” Gangakhedkar said. “Things are gradually being lifted so we don’t add a lot of infections.”

Authorities have also worked to provide more treatment resources, which could have helped limit severe infection and mortality, said Jameel. The federal government airlifted doctors from the Central Armed Police Forces to Delhi in November, doubled mobile testing capacity, and made 300 additional ICU beds available in the city.

Don’t get too comfortable

The drop in cases looks promising, but experts are warning the public not to get complacent or rely too much on official case numbers.

“In India, we also have states where the data that comes in is not as reliable,” Shewade said. “We shouldn’t praise states that are reporting less. States like Bihar aren’t doing well. They’re just not reporting cases or deaths.”

Bihar health authorities did not respond to a request for comment.

And just because the national total in daily new cases is declining, it doesn’t mean the situation is improving everywhere. The state of Maharashtra is currently seeing a resurgence in cases and issued fresh restrictions on February 19, including new rules for home quarantine, strict penalties for not wearing masks in public and the lockdown of any building with more than five positive cases.

After issuing the new restrictions, Maharashtra Chief Minister Uddhav Thackeray warned that the state could reimpose lockdown if daily new cases continued to rise in the next two weeks.

Experts are also concerned that the low number of reported cases could cause a false sense of security before the crisis has fully ended. It’s too early to relax restrictions and protective measures, they say, especially with the threat of new coronavirus variants that have been spotted in many countries.

“There is complacency all around us,” Jameel said. “Vaccine derived protection is not available to most since only select groups are getting those. Further, the second dose is rolling out only now. But if a fast moving variant starts community transmission, the dynamics could change very quickly.”

“Hopefully these (variant) strains will not cause catastrophic situations, but the vigil to contain this disease must continue.”