Over two third Indians (67.6 per cent) have COVID-19 antibodies but one third (close to 40 crore) are still susceptible to SARS- CoV-2 according to the findings of the fourth national COVID-19 sero-survey conducted by the Indian Council of Medical Research.
The sero-survey was conducted in the same 70 districts across 21 states as the first three surveys but included children between 6-10 years of age that were not included in the earlier surveys. The total number of participants stood at 28,975.
Close to 62.2 per cent of the 20,284 adult population was unvaccinated while close to 25 per cent had received one dose. Only 13 per cent were fully vaccinated.
Proving the role of vaccines in providing protection and creation of antibodies, 89.8 per cent of the fully vaccinated showed prevalence of COVID-19 antibodies. From those who received one dose, 81 per cent were sero-positive and 62 per cent of the unvaccinated were also found to have antibodies.
This fourth survey conducted in the last ten days of June and the first week of July 2021 shows a three-fold rise from the third survey conducted in December 2020 and January 2021. This increase from 21.5 per cent to 67.6 per cent is attributable to vaccination that started from March 2021 as well as the second wave witnessed across the country in the months of April and May 2021.
From the remaining participants 2,892 were between the ages of six to nine, and 5,799 were between ten to seventeen.
Surprisingly, almost half of the children between ages 6-17 were seropositive. An age-wise disaggregation in the table below shows that along with vaccination, the spread of the infection has also accounted for the increased sero-prevalence in the country.
| Age | Sero-prevalence (in %) |
| 6-9 | 57.6 |
| 10-17 | 61.6 |
| 18-44 | 66.7 |
| 45-60 | 77.6 |
| > 60 | 76.7 |
The proportion of sero-positive females was higher than that of males. Sero-positivity was also higher in the urban areas over the rural areas.
The study also included 7,252 health care workers of which 85 per cent were detected with COVID-19 antibodies.
Even though the government's intention is to fully vaccinate the healthcare workers first and even started vaccinating them from January 16, 2021, close to 10.5 per cent of the surveyed health care workers were unvaccinated. Around 13.6 per cent had received a single dose, and 76 per cent were fully vaccinated.
Dr. Balrama Bhargava, Director General of ICMR noted that India can not be complacent as one third of its population still continues to stay susceptible to the virus. He also emphasised on the need for state-level sero-surveys to address the heterogeneity they observed in this survey. However, he did not share a state-wise sero-positivity list.
The ICMR believes that only the fully vaccinated should travel across the country and that people should continue to abide by the non-pharmaceutical interventions of masking, physical distancing, and personal hygiene to tackle the virus.
The government will try to ensure that most of the vulnerable groups will be vaccinated to prevent hospitalisations or infections.