One in 5 Indians exposed to coronavirus, says sero survey

At least one in five (21%) Indians above the age of 18 years has been exposed to the coronavirus, according to Indian Council of Medical Research’s (ICMR) third nationwide sero survey that tested samples from 28,589 people for antibodies between December 17, 2020 and January 8, 2021. Among health care workers, the seroprevalence was 25.7%.

The numbers represent a sharp jump from the previous rounds — the first sero survey (conducted in May-June 2020) showed 0.73% seroprevalence, while the second one (August-September, 2020) showed overall prevalence of 6.6%. A serological test is to detect whether a person has antibodies to the Sars-Cov-2, which would indicate a past infection.

Experts said the findings of the report show that a large proportion of the country – nearly 80% – remains susceptible to the virus.

In children between the ages of 10 and 17, the prevalence was 25.3%, and people above the age of 60 showed a prevalence of 23.4%, the report showed. In the general population, the prevalence was higher in urban slums (31.7%), followed by non-urban slums (26.2%), and rural areas (19.1%).

More women had antibodies compared to men, with a prevalence rate of 22.7% and 20.3% respectively.

In the general population, 28,589 individuals were tested for antibodies against Sars-CoV-2, the virus that causes Covid-19. Additionally, 7,171 health care workers were also covered. The second group included hundred health care workers each from taluk hospitals, community health centres, primary health centres, etc, for each district covered in the country.

Doctors and nurses were affected the most with a seroprevalence of 26.6%, followed by paramedical staff (25.4%), field staff (25.3%), and administration staff (24.9%).

Presenting the findings of the report at a media briefing, ICMR director general Dr Balram Bhargava pointed out that a large proportion of people remained susceptible to catching the infection.

Experts echoed the views. “If 20% of the country has been exposed, then there are 80% who are still not exposed to the virus. That means we cannot afford to drop our guard. Covid vaccination has just started and there is still time before a significant percentage of population develops antibodies against the virus,” said Dr GC Khilnani, former head, pulmonary medicine department, All India Institute of Medical Sciences, Delhi.

The findings released on Thursday are from the third round of pan-India sero surveys conducted by ICMR. It was conducted in the same 700 villages, 70 districts from 21 states that were selected during the first and the second round of surveys, ICMR said.

“(The results of the latest sero survey) reflect the situation in the pre-vaccination period as vaccination drive started on January 16. The most sensitive test was used, and it was the same test that was used in the United States and showed the sero prevalence of 14.3%,” said Dr Bhargava.

“A large population still remains vulnerable to the virus, and vaccination is the key along with Covid-19 appropriate behaviour to stop the spread of the virus,” he added.

More than 4.6 million doses of Covid-19 vaccines have already been administered across the country in the past 18 days. Of the roughly 9.7 million (9,631,637) health care workers registered to be given a jab against Covid-19, about 45% (4,391,826) have received the first dose of the vaccine so far.

“We had estimated the number to be 10 million but when health care workers database was created on Co-WIN then it turned out to be 9,631,637 health care workers in all. So, this is the number that needs to be given both the doses of Covid-19 vaccine in the initial phase,” said Rajesh Bhushan, Union health secretary.

Thirteen states have covered at least 50% of their health care workers. Madhya Pradesh leads the states with 73.6% of health care workers being given the first dose in 18 days. It is followed by Rajasthan that has immunised 67% of its health care workforce, according to data from the Union health ministry.

Some states are yet to catch up; and there are 11 such states that have not been able to vaccinate more than 30% of its health care workers. Puducherry is still at 12.6%, followed up Manipur at 12.8%, and Meghalaya at 15.2% of its health care workers. Among bigger states, Tamil Nadu is also currently at 23.7%.