Individual SARS-CoV-2 neutralizing antibody immunity lasts from days to decades

Scientists from Duke-NUS Medical School, the National Center for Infectious Diseases (NCID) and the Agency for Science, Technology and Research (A * STAR) Laboratories for Infectious Diseases have found that antibodies to SARS-CoV-2 decrease at different rates, which lasts up to only a few days in some individuals, while they have been present in others for decades. The study, published in The Lancet microbes, shows that the severity of the infection can be a deciding factor in having longer-lasting antibodies. People with low levels of neutralizing antibodies can still be protected against COVID-19 if they have robust T-cell immunity.

The team followed 164 COVID-19 patients in Singapore for six to nine months and analyzed their blood for neutralizing antibodies against SARS-CoV-2, T cells and immune system signaling molecules. They then use this data to set up a machine learning algorithm to predict the trajectories of humans’ neutralizing antibodies over time.

The key message from this study is that the longevity of functional neutralizing antibodies to SARS-CoV-2 can vary widely, and it is important to monitor this on an individual level. This work may have implications for the longevity of immunity to vaccination, which will be part of our follow-up studies, “said Professor Wang Linfa, of Duke-NUS ‘Emerging Infectious Diseases (EID) Program, a corresponding author of the study.

The team was able to categorize people into five groups, depending on how long their antibodies lasted. The first group, which never developed detectable neutralizing antibodies, also called the ‘negative’ group, made up 11.6 percent of the patients in the study. The ‘rapidly declining’ group (26.8 percent) had early levels of rapidly declining antibodies. The ‘slowly declining’ group (29 percent) tested positive for antibodies at six months. The ‘persistent’ group (31.7 percent) showed little change in their antibody levels up to 180 days, and eventually the ‘delayed response’ group (1.8 percent) showed a marked increase in neutralizing antibodies during late recovery.

While this study focused on determining the levels of neutralizing antibodies, which are part of the body’s comprehensive immune system, the other important aspect of an effective immune system is the immunity of T-cell. The study found that the patients tested, including those from the ‘negative group’, showed persistent T-cell immunity six months after the initial infection. This shows that individuals can still be protected if they have robust T-cell immunity when the neutralizing antibody is low.

“We are investigating the neutralization of antibodies that are important for protection against COVID-19. We have found that antibodies against SARS-CoV-2 decrease at different doses in different people. This emphasizes the importance of public health and social measures in “The persistent response of the pandemic outbreak. However, the presence of T-cell immunity offers hope for long-term protection, which will require more studies and time to confirm epidemiological and clinical evidence,” said David Lye, director of the Office of Infectious Disease Research and Training, NCID, said a corresponding author of the study.

“This study reminds us that we all respond differently to infection and that different people produce different protective immune responses. Understanding the basis of these differences will help build better vaccines,” said Professor Laurent Renia, CEO of A * STAR Infectious Diseases Labs, added.

The findings are important as policymakers design vaccination programs and strategies to exit pandemics. The rate of decrease in antibodies suggests that reinfection may occur in subsequent waves of infection. As immunization provided by vaccinations decreases like naturally produced antibodies, the administration of vaccines may be necessary to prevent future outbreaks of COVID-19. Further research is needed to make this clear as vaccine programs are introduced.