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The story so far: Since the pandemic began in 2020, the Indian Council of Medical Research (ICMR) conducted three countrywide serosurveys to measure the spread of infection due to the SARS-CoV-2 virus
Serology surveys
- It take blood samples from participants and measure antibodies to check past exposure to the virus.
- From about 10 days after infection, antibodies grow to sizeable numbers in most patients.
- As some studies show, they start to decline after five to six months.
- Researchers are more interested in a class of antibodies called Immunoglobulin G (IgG), that persist the longest and latch onto the coronavirus to prevent them from proliferating and so their longevity and numbers are proxies to immunity against future infection.
- Because the SARS-CoV-2 virus is new, there is uncertainty on how long these antibodies actually last.
- Serology surveys are thus a crude measure of what proportion of a population is likely to be protected from a second infection; this can be used by planners to decide on future health-care capacity and opening up the economy.
Number of Serology survey
- The ICMR has conducted three national serology surveys since May 2020 and found that the exposure to the virus was several times that reported by confirmed cases.
- The third serosurvey that measured the spread of infection from December to early January found that 21.5% of India’s adult population and 25% of those between 10-17 years old may have been infected.
- Before that in August-September, it was 7% and the first survey, May-June 2020 estimated infection rate at 0.73%.
Source: The Hindu
