The fourth round of the national sero survey report puts the overall sero-prevalence in the country at 67.6%, leaving some 400 million or a third of the population still susceptible to the Covid-19 infection, the government said on Tuesday.
Children were included in the national survey for the first time and while those between 6 and 9 years of age showed a 57.2% sero-prevalence, for those between 10 and 17 years, this was 61.6%, according to the Indian Council of Medical Research (ICMR).
The government said 85% of the surveyed healthcare workers had antibodies against SARS-CoV-2 while a tenth remains unvaccinated.
The highest sero prevalence of 77.6% was seen among those between 45 and 60 years, followed by 76.7% in the above 60 age group. Around 66.7% of those between 18 and 44 years showed sero-prevalence, the ICMR report showed.
Balram Bhargava, director-general, ICMR, said there was no room for complacency as a third of the population still did not have any antibodies, so 400 million remain vulnerable. States, districts and areas without antibodies run the risk of infection waves.
VK Paul, member (health), Niti Aayog, said the rise in sero-prevalence from 24.1% in the third round to 67.6% in the fourth round was the result of the second wave and the delta variant of the virus. A part of the sero positivity could also be due to the vaccination.
The survey was conducted in the last 10 days of June and the first week of July, across 70 districts in 21 states, and in the same places as the first three sero surveys. It covered 28,975 people, with children accounting for 30% of those surveyed. It covered 20,284 adults and 7,252 were healthcare workers.
Among the adult population surveyed, around 62.2% were not vaccinated and only 13% had received two vaccine doses while 24.8% received only their first dose. The unvaccinated showed sero-positivity of 62.3%. Those who had received both doses of the vaccine had 89.8% sero prevalence, while those with a single dose were at 81%. The sero-prevalence in urban and rural areas was similar.