New Delhi: A sero survey carried by the Delhi government showed that 79 of 257 people, who had coronavirus, did not have antibodies in them after a few months.
However, there is no need to panic as memory cells will trigger an immune response in most cases, say experts. Also, neutralising antibodies (IgG) tend to vanish after three months.
“The people who had COVID-19 and recovered and did not show antibodies during the survey might have contracted the disease four or five months back at the initial stage of infection. Now their antibodies (IgG) might have disappeared. We will have to study their individual cases deeper to understand it better,” an official source told The Hindu.
The survey tested blood samples of about 15,000 random people.
“IgG falls and it is a normal biological mechanism. But, if the virus attacks the body again, then the memory cells will kick in and they will trigger IgG which will give immunity in most people with some exception and people with immunodeficiency (inability to produce an adequate immune response),” said Jayaprakash Muliyil, epidemiologist and former principal of Christian Medical College, Vellore.
“The virus may revisit you and be transiently present in your throat, but it will almost never be able to produce a disease,” he added.
K. Srinath Reddy, epidemiologist, and president of Public Health Foundation of India (PHFI), Delhi also said the same. “In most cases, the antibodies (IgG) decline by three months, but memory B cells and memory T cells store the memory of the virus. They activate the immune mechanism when there is a re-infection. So, antibodies vanishing doesn’t mean that you are totally vulnerable to the virus,” Reddy said.
He also pointed out that the virus can invade the body and reach nose or throat of a recovered person and this person will test positive for COVID-19 if he takes a nasal swab test. But, memory cells will act and mount an immune response to prevent the infection from turning into a disease for most people, he added.