In its second sero-survey conducted between August 17 and September 22, 2020, the Indian Council of Medical Research (ICMR) found that around 6.6% of the 29,082 participants were exposed to SARS-CoV-2. The participants were taken from 700 areas in 70 districts across 21 states of the country.
The ICMR included participants between 10-18 years of age as they had seen a prevalence of COVID-19 among people belonging to this age group. One in every 15 individuals was estimated to have been exposed to the virus. Sero-surveys are conducted to test for the presence of antibodies against a particular antigen.
The first sero-survey was conducted only among people older than 18. Comparing to the parameters of the first sero-survey, 7.1% of the participants over 18 years of age were exposed to the virus. In the first sero-survey, only 0.73% of the participants were exposed to the virus. The second round showed that the proportion of people who were exposed to SARS-CoV-2 has increased by 6.4%. The first sero-survey to assess the presence of IgG antibodies was conducted between May 11 and June 4, 2020. There was no significant difference in the prevalence on the basis of age or gender, according to the survey.
Dr. Balrama Bhargava, Director General, ICMR insisted that these surveys only show trends of exposure and do not necessarily reflect that all these participants were infected by COVID-19. The results are yet to be published in the Indian Journal of Medical Research, ICMR's journal for publishing medical research.
Speaking about the effectiveness of scaling up testing and treating, Bhargava said that the number of infections per diagnosed case decreased from 81-130 for each case in May to about 26-30 in August. India raised its testing capacity to over 15 lakh tests and has been conducting between 7-14 lakh tests daily. Health secretary Rajesh Bhushan informed that the fluctuation in testing should not worry the country's population as the seven-day rolling average number of tests was increasing.
Urban slums with a prevalence of 15.6% and non-slum areas with a prevalence of 8.2% were found to have a higher prevalence than that of rural areas. The sero-positivity in rural areas was found to be 4.4%. People residing in the urban slums had four times the risk of being exposed to the coronavirus than the ones inhabiting rural areas. The ICMR recommended that interventions should be specially designed to target the spread of the disease in the urban slums across all the cities.
Containment Zones
The ICMR faced ire after it was revealed that the apex body asked its researchers to not publish the data from the metropolitan cities and containment zones. Bhargava compared the results of the second-survey with the existing sero-surveys conducted across Delhi, Mumbai, Ahmedabad, Puducherry, Chennai, and Indore. Delhi and Mumbai showed a higher prevalence than the findings of the second survey suggesting that more people have been exposed to the virus in these areas.
Sero-Prevalence Higher Than Other Countries
India with over 6.22 million cases has shown the fastest spread of COVID-19. The sero-survey findings further supported this finding. India's sero-prevalence is higher than Brazil (2.8%) and Spain (4.6%), said Dr. Bhargava. Iran with 22% and US with 9.3% showed higher sero-prevalence than India.
Indians Should Not Exhibit Prevention Fatigue
Dr. Bhargava added that Indians are still susceptible to the virus as a majority of the population was still unexposed to the virus. He requested that citizens continue following social distancing measures in the country and fall prey to "prevention fatigue". He emphasised that citizens should continue wearing masks and practising hand hygiene to curb the transmission of the virus.
In the press conference, all the officials insisted that citizens need to be more vigilant and take precautionary measures as the festival season is set to begin in the country. Dr. Vinod Paul, member NITI Aayog also highlighted that the respiratory viruses tend to spread faster during winter and thus precautionary measures should be followed even during that period.
