Explainer: Two-thirds of the people in the country have become cowardly? What does Sero Survey really mean? | Explainer

The ICMR said in a recent CERO survey that two-thirds of Indians may have contracted corona. What exactly do they do in this Sero survey and does that mean we got Herd immunity?

New Delhi, July 21: By the Indian Council of Medical Research (Indian Council of Medical Research – ICMR) According to a recent serological survey, about 68 per cent of Indians over the age of six have Covid-19.Covid19) The infection may have gone away and they may have recovered from it. Novel Coronavirus (Novel Coronavirus) Of course antibodies that work against the corona virus (Antibodies Survey) The survey traces how many people have formed in their bodies. This is a useful tool for measuring the spread of the disease. It is widely assumed that the number of coronaviruses will be much higher than the numbers that have emerged from the tests. Let’s take a look at this sero survey.

How many national level surveys have been conducted in India?

– First National Level Sero Survey (National Sero Survey) It happened in May 2020. Of those who were tested at the time, only one percent had antibodies against the corona. The fourth and latest National Sero Survey of ICMR was conducted in June-July 2021. The fourth survey was conducted in 70 districts in 21 states where the first three surveys were conducted. In the fourth phase, 28,975 people were tested.

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A second CERO survey, launched in August 2020, found antibodies in 6.6 percent of people. A third survey, conducted between December 2020 and January 2021, found that antibodies were found in about one-fifth of individuals. This means that so many people were infected with Kovid-19 and many of them were infected. The third survey included individuals over 10 years of age, while the fourth survey included all individuals over six years of age.

Why are CERO surveys conducted?

– CERO surveys are conducted to determine the percentage of the population infected with the corona virus, the ICMR said. It also includes asymptomatic coronary artery disease.

Of course, that is not all. This can be used to estimate the risk of infection in a high-risk population compared to other populations. E.g. Health workers, frontline workers, people with low immunity, etc.

Therefore, it may be possible for the health system to take appropriate action according to the group concerned.

World Health Organization (WHO) chief scientist Dr. According to Dr Saumya Swaminathan, the CERO survey also provides an opportunity to find out how long a person’s immunity lasts after becoming covid-19. If a sero survey of the same group is taken at regular intervals, it is possible to understand how much immunity has been developed against the virus.

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Importantly, no one has been infected with the corona virus yet, according to the CERO survey. Therefore, it is possible to estimate which population group is still at risk of infection and how many goals that group needs to achieve until they achieve herd immunity.

Has herd immunity developed in India?

– If enough antibodies have been developed against the infection in a sufficient population in a certain group of the population, further spread of the disease can be stopped. Because he can’t find new people to infect. These antibodies may be caused by a related disease or produced by vaccination. This condition is called herd immunity. Heard immunity protects other people who do not have antibodies from infection.

Heard immunity?

Herd immunity varies from disease to disease. In the case of highly contagious diseases like measles, herd immunity should be 94%. That means 9 out of 10 people must have either recovered from the disease or been vaccinated; But since vaccination against other diseases, such as measles, is very common, we do not see the widespread prevalence of such diseases. Rare cases are seen.

In the case of corona virus, herd immunity is expected to be 70 to 80 percent. This means that four out of every five people should have antibodies against it; However, experts say that it is not easy to reach this level in the case of an infection that has never been detected before.

Also, herd immunity can be dimmed if new strains arrive. Also, if a strain has the ability to neutralize antibodies produced by the vaccine, it is difficult to obtain herd immunity.

Announcing the findings of the fourth CERO survey, ICMR Director General Dr. Dr Balrama Bhargava said, “Two-thirds of the population over the age of six is ​​infected with the corona virus. One third of the population does not have antibodies. As a result, 400 million people in the country are still at risk of infection.

The high population of antibody-producing populations is a ray of hope; However, he said there was no alternative but to take adequate care as India has not yet developed herd immunity.

What exactly is done in the CERO survey?

– According to the information provided by ICMR, the CERO survey looks for the production of IgG antibodies in the body of the person concerned. These antibodies appear in the body two weeks after the onset of the infection and after the person has completely recovered from the infection. They last for many months. Therefore, a fresh infection cannot be diagnosed from a sero survey.

Infection can be detected by RT-PCR or Rapid Antigen Test (RAT). For this, a swab sample is taken through the nose or throat. At that point, the actual virus is discovered. A blood sample is taken to check for antibodies during a sero survey. It does not detect the presence of viruses, but the presence of antibodies.

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If the antibody test is reactive, then the antibodies are present and if non-reactive, then they are non-existent.

Which antibodies are detected in the test?

– Ig in IgG means immunoglobulin. It is a class of proteins and acts as antibodies. These proteins can be found in the blood as well as in the immune system. Sero surveys are conducted in India to find out the immunoglobulin. According to experts, 70-80 percent of immunoglobulins in the blood are IgG type.

In the early stages of infection, the body can produce certain types of IgG antibodies. This provides long lasting protection from the relevant microorganisms.

According to the Fourth Sero Survey, antibodies were found in 62.3 percent of unvaccinated individuals. Antibodies were found in the bodies of 81 percent of people who took a single dose of the vaccine. Antibodies were found in the body of 89.8 percent of those who took both doses.

First published:July 21, 2021, 5:07 PM IST

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