The third countrywide sero survey conducted by the Indian Council of Medical Research showed that 21.5% of the country’s population has been exposed to the coronavirus, PTI reported on Thursday.

In a press conference, Balram Bhargava, the director general of ICMR, said the results of the sero survey showed that a large population in India remains vulnerable to the infection.

The survey was conducted between December 17 and January 8, he said. It included a general population of 28,589 people as well as 7,171 healthcare workers.

According to the US’ Centers for Disease Control and Prevention, serology tests are “those that look for antibodies in blood”. “If antibodies are found, that means there has been a previous infection,” it says. “However, there is a chance a positive result means that you have antibodies from an infection with a virus from the same family of viruses (called coronaviruses), such as the one that causes the common cold.”

Serological surveys reveal how many people may have been infected with the novel coronavirus in an area but they do not show how many people are immune to the virus. It still isn’t clear how long antibodies last in infected persons and how many antibodies are needed to protect a person from reinfection.

Second dose of vaccine for health workers from February 13

During the press conference, VK Paul, a member of think tank NITI Aayog, also announced that the second dose of the coronavirus vaccine will be administered to healthcare workers from February 13, reported News18.

The coronavirus vaccination drive began on January 16. Healthcare have been given just the first dose of the vaccine so far.

On the vaccination drive, Health Secretary Rajesh Bhushan said that India was the fastest country in the world to inoculate 4 million (40 lakh) people. “We took 18 days to vaccinate 4 million people,” he said. India has so far vaccinated 45,93,427 beneficiaries till 1.30 pm on Thursday, the health secretary added.

The Union Health Ministry said that it was a matter of concern that the weekly positivity rate of eight states and Union Territories were more than the country’s average positivity rate. These states are Kerala (11.20%), Chhattisgarh (6.20%), Maharashtra (4.70%), Goa (4.40%), Nagaland (3.60%), Ladakh (2.90%), Puducherry (2.60%) and Chandigarh (2.10%). India’s positivity rate is 1.82%.

Source: Union Health Ministry

The ministry added that in the last three weeks, 47 districts have not reported any new Covid-19 cases, while 251 districts have not reported any fatalities. Union Health Secretary Rajesh Bhushan said that the daily coronavirus cases and deaths were continuously declining.

India reported 12,899 new coronavirus cases on Thursday, taking its tally to 1,07,90,183. Deaths rose by 107 to 1,54,703. As many as 1,04,80,455 people have recovered from the infection so far. The active cases remained below the 2 lakh mark at 1,55,025 for the 16th consecutive day.