In a new study, researchers found that antibodies against SARS-CoV-2 wane at different rates, lasting for mere days in some individuals while remaining present in others for decades.
They found that the severity of the infection could be a deciding factor in having longer-lasting antibodies.
Individuals with low levels of neutralizing antibodies may still be protected from COVID-19 if they have a robust T-cell immunity.
The research was conducted by scientists from Duke-NUS Medical School and elsewhere.
In the study, the team followed 164 COVID-19 patients in Singapore for six to nine months, analyzing their blood for neutralizing antibodies against SARS-CoV-2, T cells and immune system signaling molecules.
They then used this data to establish a machine-learning algorithm to predict the trajectories of peoples’ neutralizing antibodies over time.
The team found the longevity of functional neutralizing antibodies against SARS-CoV-2 can vary greatly and it is important to monitor this at an individual level.
They categorized people into five groups depending on how long their antibodies lasted.
The first group, who never developed detectable neutralizing antibodies also called the ‘negative’ group, comprised 11.6% of the patients.
The ‘rapid waning’ group (26.8%) had varying early levels of antibodies that waned quickly. The ‘slow waning’ group (29%) tested mostly positive for antibodies at six months.
The ‘persistent’ group (31.7%) showed little change in their antibody levels up to 180 days and, finally, the ‘delayed response’ group (1.8%) showed a marked rise in neutralizing antibodies during late convalescence.
While this study focused on determining the levels of neutralizing antibodies, which are part of the body’s comprehensive immune defense system, the other important aspect of an effective immune defense is T-cell immunity.
The study found that the patients tested, including those from the ‘negative group’, displayed sustained T-cell immunity six months after the initial infection.
This shows that individuals may still be protected if they have a robust T-cell immunity when the neutralizing antibody level is low.
The findings are important as policymakers design vaccination programs and pandemic exit strategies. The rate of antibody waning suggests re-infection may occur in subsequent waves of infection.
Also, if immunity provided via vaccinations wanes like naturally-produced antibodies, then annual vaccine administration could be necessary to prevent future outbreaks of COVID-19.
Further research will be needed to clarify this as vaccine programs are rolled out.
The study is published in The Lancet Microbe. One author of the study is Professor Wang Linfa.
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