This colorized scanning electron microscope image shows SARS-CoV-2 (round blue objects), the virus that causes COVID-19, emerging from the surface of cells cultured in the lab. [Image courtesy of National Institute of Allergy and Infectious Diseases]
The study followed 164 patients infected with the novel coronavirus for up to 180 days after symptoms developed, measuring changes in neutralizing antibody levels.
The researchers at the Duke–National University of Singapore (Duke–NUS) then used a machine learning model to predict neutralizing antibodies’ duration.
After concluding that such antibodies’ presence varies widely in individuals, Wang Linfa, a professor at Duke-NUS and a corresponding author of the study, theorized that it is vital to monitor neutralizing antibody levels in individuals over time. “This work may have implications for immunity longevity after vaccination, which will be part of our follow-up studies,” Wang Linfa said in a statement.
The researchers broke study participants into the following groups:
- A total of 11.6% of study participants did not develop detectable levels of neutralizing antibodies.
- Some 26.8% saw their antibody levels decline quickly.
- Another 29.0% generally tested positive for antibodies at six months.
- A total of 31.7% had significant neutralizing antibody levels up to 180 days after developing COVID-19 symptoms.
- A ‘delayed response’ group (1.8%) developed neutralizing antibodies during a late stage of recovery from infection.
In general, participants who had persistent neutralizing antibodies tended to have more severe infections accompanied by substantial levels of cytokines and growth factors.
The study authors also observed the presence of T-cell immunity across study participants, including those without detectable neutralizing antibodies. According to Dr. David Lye, a professor at National Center for Infectious Diseases in Singapore, more data are required to understand the protection afforded from T-cell immunity in the long term.
The study findings could help drug companies develop better vaccines, according to Laurent Renia, executive director of A*STAR Infectious Diseases Labs.
The study could also help policymakers formulate strategies for ending the pandemic and preventing potential waves of reinfection resulting from waning immunity.
However, the study authors stress that they are “not at a stage to conclusively correlate the level of antibody responses with protective immunity” but added that the research has shed light on the dynamics of antibody responses from COVID-19 infection.
The antibody response to other coronaviruses that infect humans is generally short-lived.
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