Covid-19 antibodies could last from days to decades based on infection severity

A new study has revealed that antibodies against Covid-19 may vary from person to person. In some, the antibodies last for some days, while in others, they can last for decades.

The potential of antibodies largely depends on the Covid-19 infection severity, according to the study published in the journal Lancet Microbe.

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The study noted that recovered patients from coronavirus with low levels of neutralising antibodies may still be protected from reinfection if they have robust immunity in the form of the body’s T-cells.

For the study, the researchers, including those from Duke-NUS Medical School in Singapore, followed 164 Covid-19 patients for six to nine months. The researchers examined their blood for neutralising antibodies against the SARS-CoV-2 virus, their T-cells, and immune system signalling molecules.

The researchers further used the information to train a machine-learning algorithm to predict the trajectories of people’s neutralising antibodies over time.

Furthermore, the researchers made five cohorts of the recovered patients based on how long their antibodies lasted.

The first group included those who never developed detectable neutralising antibodies — also called the ‘negative’ group — comprising 11.6 per cent of the patients in the study.

The ‘rapid waning’ group, which included 26.8 per cent of the patients, had varying early levels of antibodies that waned quickly, the scientists said.

According to the researchers, the ‘slow waning’ group, which included 29 per cent of the participants, tested mostly positive for antibodies after half a year.

The ‘persistent’ group, comprising 31.7 per cent of the individuals, showed little change in their antibody levels up to 180 days. The researchers said that the ‘delayed response’ group (1.8 per cent) showed a significant rise in neutralising antibodies during late convalescence.

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Corresponding author Professor Wang Linfa, from Duke-NUS’ Emerging Infectious Diseases (EID) Programme, said: “The key message from this study is that the longevity of functional neutralising antibodies against SARS-CoV-2 can vary greatly and it is important to monitor this at an individual level.”

“This work may have implications for immunity longevity after vaccination, which will be part of our follow-up studies,” Linfa added.

According to the study, patients, including those from the ‘negative group’, displayed sustained T-cell immunity six months after the initial infection. This means that individuals may still be protected if they have a robust T-cell immunity when the neutralising antibody level is low.

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