After almost three months, the Indian Council of Medical Research (ICMR) has published the findings of part two of the first national population-based serosurvey conducted between May 11 and June 4 to assess the prevalence of COVID-19 in the country.
A total of 30,283 households were visited and 28,000 individuals were enrolled from 21 states. About one-fourth of the surveyed clusters were from urban areas.
The seropositivity rate was highest at 69.4 percent in the rural areas while in urban slums it was 15.9 percent and in urban non-slums,14.6 percent.
Serosurveys provide important estimates of the total number of infections in the country. “Based on the overall adjusted seroprevalence of 0.73 per cent and reported number of COVID-19 cases, it was estimated that for every RT-qPCR confirmed case of COVID-19, there were 82-130 infections in India,” the survey said.
The ‘low’ prevalence observed in most districts indicates that India is in early phase of the epidemic and the majority of the Indian population is still susceptible to SARS-CoV-2 infection, it added.
The ICMR had shared initial data on 11 June from the serosurvey conducted in collaboration with the state health departments, NCDC and WHO India. For part one, 15 districts each were selected from four groups (zero cases, low incidence, medium incidence and high incidence). The blood samples and data were collected from a total of 26,400 individuals.
The findings had revealed that the infection fatality rate is under 1%. ICMR Director-General Balram Bhargava said at the press briefing, “We have to work on the non Pharmacological Interventions such as physical distancing, use of face mask/cover, hand hygiene, cough etiquette. Local lockdown measures need to continue.”
It’s important to note that antibody tests are not diagnostic tests but are used to check the prevalence of the infection in the general population. These surveys at best indicate the possible spread of the disease in the community and help authorities come up with better strategies. They show us the presence or absence of antibodies in a person - they do not tell us the amount, and they cannot identify if these are ‘neutralising’ antibodies (which specifically target the pathogen in concern).
Associating the presence of antibodies to immunity against COVID-19 is another overstretched link, experts believe. FIT had earlier reported on the danger of assuming herd immunity based on serosurvey results.
Dr K Srinath Reddy, President of Public Health Foundation of India (PHFI) had told FIT, “We do not know to what levels these antibodies will confer immunity or what duration that immunity will last. For instance, influenza immunity does not last long. We also need to know if we need cell immunity or whether these antibodies are enough.”
With reports of possible reinfections coming in from parts of the country and the world, following precautions and staying safe would still remain as crucial as ever.