New Delhi: Even as India, and the world, races ahead to launch a vaccine against Covid-19—on Saturday, Prime Minister Narendra Modi inspected three major pharmaceutical facilities in Ahmedabad, Hyderabad, and Pune in this regard—the latest ICMR survey has revealed that more than 7.43 crore Indians were already infected by the coronavirus pandemic by August 2020.
Officially, 93,51,224 coronavirus cases have been reported as of November 28. A total of 1,36,238 deaths and 87,59, 969 recoveries were reported since March.
The Indian Council of Medical Research (ICMR) had conducted the first serological survey in May and the second one recently. It found that infection doubling time at the national level was about 27 days, according to media reports.
With fresh numbers available, one in 15 individuals in India, aged 10 and above had so far been exposed to the pandemic, totaling an estimated 7.43 crore until August, according to the ICMR’s nationwide biomedical survey.
A serosurvey depends on the collection and testing of specimens from a defined population over a specified period to determine antibodies against a given etiologic agent as a direct measure of the population’s immunity.
The adult seroprevalence (level of a pathogen in a population as measured in blood serum) increased 10 times between May and August 2020, it said.
The first nationwide serosurvey was conducted in May when the whole of India was under a stringent lockdown. It showed a low prevalence of 0.73% of the infection among the general adult population.
For a second time, the ICMR conducted a cross-sectional survey between August 17 and September 22 in the same 700 clusters (villages in rural areas and wards in urban areas) from 70 districts in 21 states as it had done in the first nationwide serosurvey.
The ICMR’s findings of the second survey were published in The Lancet Global Health pre-print.
“The transmission of infection is expected to continue in most Indian states till the herd immunity threshold is achieved, either by natural infection or vaccination. While this threshold is unknown, most estimates place it above 50%,” stated the survey.
It revealed that the prevalence of Covid-19 antibodies was the highest in urban slum areas, followed by urban non-slum areas and rural regions.
One in nine persons who did not report any symptoms of the infections actually had developed the Covid-19 (SARS-CoV-2) antibodies.
The ICMR reported 26-32 infections for each Covid-19 case diagnosed in August 2020, compared to 82-131 infections per case reported in the first national serosurvey.
“Lower infection to case ratio in August compared to May reflects a substantial increase in testing across the country.” It advocated increased testing to cover even people without any known exposure or symptoms.
“Our data supports the expansion of testing strategies to include individuals without having known exposure or symptoms.”
Only 3% of the people showing the prevalence of antibodies against the novel coronavirus had actually reported symptoms of Covid-19.
“We found only 3% of seropositive individuals reported Covid-19 symptoms highlighting the limitations of symptom-directed testing and the importance of universal prevention methods,” the report added.