Madhya Pradesh has the highest seroprevalance, or the presence of antibodies to the novel coronavirus, and Kerala the lowest among 21 States studied, according to the Indian Council of Medical Research’s (ICMR) fourth national serology survey. Though headline results of the survey were published last week, the State-wise approximate prevalence was issued on Wednesday.
Kerala, which is recording the sharpest rise in cases in the country fuelled by the Delta variant, had a seroprevalence of only 44% implying 56% lacked antibodies — and consequently — remained vulnerable to the infection. The antibody levels reported State-wise as part of the ICMR survey didn’t distinguish between those in response to a natural infection or through vaccination.
Madhya Pradesh has a seroprevalence of 79%, followed by Rajasthan (76%) and Bihar (75%). After Kerala, the least antibody prevalence was in Assam (50%) and Maharashtra (58%).
‘Partial’ picture
An ICMR official said State seroprevalence gives a ‘partial’ picture of how they are affected. “The extrapolation was based on 70 districts in 21 States, which were part of three previous rounds of the serosurvey. The districts were chosen based on population and so some States have more places represented,” said Samiran Panda, who was involved with the survey and who heads the epidemiology division at the ICMR.
Explained | Why are serology surveys important?
“The ELISA test used to check antibodies also has a role in marking antibody prevalence. This also suggests that States that may have managed the infection better in the first and second wave, and protecting a large fraction from infection, must also target rapid vaccination to protect the remaining vulnerable.”
The Centre on Wednesday advised all States/UTs to conduct the surveys in consultation with the ICMR to generate district-level data which was critical to formulating localised public health response measures, according to a letter by Rajesh Bhushan, Health Secretary, on Wednesday.
The 4th National Sero-Prevalence Survey done by the ICMR said such studies could follow a standardised protocol, whose findings could be utilised quickly by the respective State/UT to “guide objective, transparent and evidence-based public health response to COVID-19”.
While two-thirds of the general population have SARS-CoV-2 antibodies, making approximately 40 crore people still vulnerable to infections, ICMR Director General Balram Bhargava said last week while presenting the survey results. States, districts and areas without antibodies run the risk of infection waves. The same survey also showed that antibodies could be detected in over 88% of those vaccinated with at least one dose, though State-wise reports aren’t yet available as the survey is yet to be formally published in a scientific journal.
Similar in rural, urban areas
The survey also noted that more than half of the children (6-17 yr) were seropositive while sero-prevalence was similar in rural and urban areas. It was also found that 85% of health care workers (HCWs) had antibodies and nearly one-tenth were unvaccinated.
“The national sero-survey by ICMR was designed to capture the extent of the spread of COVID infection at the national level. Therefore, the results do not reflect the heterogeneity of sero-prevalence between districts and even between States,” the Health Ministry said in an accompanying statement.
Published - July 28, 2021 10:15 pm IST
