Roughly two-thirds of all Indians over six, or 67.6 per cent of the population, have antibodies against the coronavirus, the government said as it announced the results of the fourth serosurvey.

This means around 40 crore (400 million) are still at risk of infection, the government added, as it warned against laxity in following Covid-appropriate behaviour and urged eligible people to get vaccinated.

"The fourth serosurvey shows there is a ray of hope, but there is no room for complacency. We must maintain Covid-appropriate behaviour," ICMR chief Dr Balram Bhargava said.

A survey of 36,227 people, including 7,252 healthcare workers, conducted across 70 districts in 21 states in June-July indicated 67.6 per cent of Indians over the age of six had COVID-19 antibodies.

Over 50 per cent of 8,691 children between the age of six and 17 who were tested also had the antibodies. This was the first national survey to test for antibodies in those under the age of 18 - a decision taken amid widespread concern that future waves could affect children, NDTV said. 

Last month a survey in Mumbai showed 51.18 per cent of those below 18 had COVID-19 antibodies.

The 67.6 per cent figure is a steep increase from the results of the third serosurvey. 

Conducted in December-January, shortly before the second wave began, it suggested that only 21 per cent of those over 10 showed evidence of past exposure to COVID-19.

The second and first serosurveys, conducted last year in August-September (during the first wave of infections) and May-June, respectively, returned 7.1 and 0.7 per cent indications.

The results of the fourth serosurvey suggest the virus has covered around 67 per cent of India's population in a year - despite the centre imposing one of the world's strictest lockdowns and states following that with a slew of localised restrictions, some of which are still in place.

Medical experts and doctors have repeatedly warned of a third wave of infections and deaths, particularly since the second brought the country's healthcare system to its knees, NDTV said.

However, images of people eschewing even the most basic protocols - wearing face masks and maintaining social distance in public - have drawn criticism and renewed fears. The government has repeatedly urged people to follow the rules, with Prime Minister Modi among the voices.

Some states' decision to allow large-scale religious gatherings has increased the potential for the virus to spread. Kerala and Uttar Pradesh have both been hauled up by the Supreme Court for allowing Bakrid (Eid-ul-Azha) and the Kanwar Yatra to be celebrated.

The circulation of more aggressive variants of the virus, including those that are potentially more resistant to the vaccines, have further heightened worries of a third wave.

Last month AIIMS (Delhi) chief Dr Randeep Guleria said it was "inevitable", and that the main challenge now is vaccinating enough people to minimise the impact.

Concerns, however, have been raised over the slow pace of daily vaccinations, which dipped from a record high of over 80 lakh doses on June 21 to a seven-day average of 38.62 lakh on Monday.

India Tuesday recorded 30,093 new cases in 24 hours - the lowest in four months. (SAM)