Antibodies against SARS-CoV-2 may not guarantee immunity, sa
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While the presence of antibodies against SARS-CoV-2 is indicative of past exposure to the virus, it is not synonymous with immunity against it, scientists have clarified.

The clarification comes as serosurveys conducted in the past have led to misconceptions about community-wide immunity.

Scientists say immunity depends on the kind of antibodies, the concentration, and how long they last.

• Antibody presence tells us nothing about disease progression: Immunologist

As scientists are trying to understand how antibodies impact the progression of COVID-19, immunologist Satyajit Rath from the National Institute of Immunology (NII) told PTI that antibody presence in itself tells us nothing about disease progression.

The only thing the presence of antibodies indicates with certainty is that an individual has been infected in the past.

• 'Antibody presence doesn't guarantee protection from disease'

Vineeta Bal from Pune's IISER told PTI Bal said, "Simple presence of antibodies is a clear indication of previous exposure to SARS-CoV-2 but does not necessarily guarantee protection from the disease in the absence of neutralizing antibodies."

She added, "Presence of nAbs in sufficient concentrations and for a longer period is the most likely indicator of protection of the individual from next exposure leading to illness i.e. COVID-19."

• No consensus on nAb levels that could offer immunity

Further, Bal said that there is no consensus on the levels of nAbs in the blood that could offer "protection" against a pathogen. Similarly, the level of nAbs required to ensure that plasma therapy is useful also remains unestablished, she said.

• 'Antibody tests in market not targeting same viral proteins'

Further, Rath noted, "All antibody tests in the market are not against the same viral protein target, and some investigators use only one target, others use more. And it is possible that tests differ in their sensitivity," adding that this creates issues with drawing out easy patterns in different serosurveys.

Most serosurveys also report results as simply "positive"/"negative" without analyzing antibody levels, he added.

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