30% recovered COVID-19 patients have no antibodies: govt. survey

‘No need to panic as memory cells will trigger immune response in most cases’

Seventy-nine of 257 people who had COVID-19, recovered, and later tested for antibodies against the virus, did not have the antibodies, according to a report of the second serological survey done in August by the Delhi government.

Experts, however, said that there was no need to “panic”, as the neutralising antibodies (IgG) tend to vanish after three months, but in most cases the memory cells will remember the virus and trigger an immune response if the person who recovered from COVID-19 is again attacked by the virus.

“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 said.

Under the survey, blood samples of about 15,000 random people were collected from August 1-7 and tested for antibodies (IgG) against the virus.

The report was prepared by Maulana Azad Medical College (MAMC), which provided technical support for the survey.

Biological mechanism

“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 be almost never able to produce a disease,” he added.

K. Srinath Reddy, epidemiologist, and president of Public Health Foundation of India (PHFI), Delhi, also had a similar opinion.

Memory cells

“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,” Dr. Reddy said.

He said that even for a person who had COVID-19 and has memory cells, still the virus can invade the body and reach nose or throat. “During this time, the person will test positive for COVID-19, if he takes a nasal swab test. But in most cases, people will have memory cells to fall back upon to mount an immune response to prevent infection from turning into a disease,” Dr. Reddy said.

The report showed that among people with income less than ₹5,000, 31.7% people of the people surveyed had antibodies, while in people with income above ₹5,000, only 26.8% people had antibodies.

Similarly, among people with BPL (below poverty line) cards, 35.4% people surveyed tested positive for antibodies, while among people who were above poverty line and did not have BPL card, only 29.4% of people surveyed tested positive. Also, a higher percentage of antibodies was seen in people living in a containment zone.