Almost one-quarter of India’s population of 1.36 billion “now have antibodies” against the Chinese coronavirus, according to a survey from the Indian Council of Medical Research (ICMR).

“Nearly 25 percent of the population or every one in four persons in India has shown evidence of past infection of coronavirus, the third national serosurvey conducted by the ICMR revealed,” according to the New Indian Express on January 31.

Serology surveys involve testing blood samples for the presence of antibodies, or specific proteins made in response to an infection that may support immunity against future infection. Antibodies against coronavirus typically form about two to three weeks after infection.

The ICMR has yet to officially release the findings of its latest serosurvey, but sources familiar with the data told the New Indian Express on Sunday that the health body is expected to announce the new results “within the next few days.”

The survey estimates that India’s “actual Covid-19 [Chinese coronavirus] infection size is 30 crore [300 million] – even as the number of confirmed cases stands at just over 1 crore [10 million],” sources confirmed to the newspaper.

“The figures are much higher in many cities, strengthening the epidemiological theory that some cities in the country may be approaching herd immunity as evident in the falling daily numbers of new cases,” an official associated with the survey told the New Indian Express.

“Like the previous two surveys, the seropositivity has been found to be way higher particularly in urban slums and generally in urban areas as compared to rural areas,” the unnamed official added.

“[N]early one in 15 individuals aged 10 years or older were exposed to SARS-CoV-2 [coronavirus] in India by Aug 18, 2020,” according to ICMR’s second serosurvey, conducted August-September 2020.

The ICMR carried out its third serosurvey from December 2020 through January 2021. It focused on “testing for antibodies against SARS-CoV-2 in blood samples of 400 randomly selected persons” in 70 districts across 22 states where the ICMR’s previous two serosurveys took place in May and August 2020.

The Indian state health body collected “samples from 100 healthcare workers from both government and private facilities in each of these 70 districts … for the antibody tests. Unlike the previous surveys that only looked for antibodies against the viral nucleocapsid, researchers in the third survey also tested for spike protein antibodies which last longer in the bloodstream,” according to the New Indian Express.

India currently has the second-highest official coronavirus caseload in the world, after the U.S. These numbers may not fully reflect the global reality as rogue states like Russia, China, and Iran have long stood accused of manipulating its coronavirus data. The South Asian giant launched the world’s largest Chinese coronavirus vaccine drive on January 19. India vaccinated half a million people within the campaign’s first day, according to the United Nations.