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

Scientists at Duke-NUS Medical School, the National Center for Infectious Diseases (NCID) and the Agency for Science, Technology and Research (A * STAR) Infectious Diseases Labs found that antibodies against SARS-CoV-2 decrease at different rates, lasting for mere days in some individuals, while remaining present in others for decades. The study, published in The Lancet Microbe, shows that the severity of the infection can be a decisive factor for the existence of antibodies of long duration. Individuals with low levels of neutralizing antibodies can still be protected from COVID-19 if they have robust T cell immunity.

The team followed 164 patients with COVID-19 in Singapore for six to nine months, analyzing their blood for neutralizing antibodies against SARS-CoV-2, T cells and immune signaling molecules. They then used this data to establish a machine learning algorithm to predict the trajectories of people’s neutralizing antibodies over time.

“The main message of this study is that the longevity of functional neutralizing antibodies against SARS-CoV-2 can vary widely and it is important to monitor this at an individual level. This work may have implications for the longevity of immunity after vaccination, which will be part of of our follow-up studies, “said Professor Wang Linfa of Duke-NUS’s Emerging Infectious Diseases (EID) Program, 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, comprised 11.6% of the patients in the study. The ‘rapid decline’ group (26.8 percent) had varying initial levels of antibodies that decreased rapidly. The ‘slow decline’ group (29 percent) tested mostly positive for antibodies at six months. The ‘persistent’ group (31.7 percent) showed little change in their antibody levels up to 180 days, and finally, the ‘late response’ group (1.8 percent) showed a marked increase 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 effective immune defense is T-cell immunity. The study found that patients tested, including those in the ‘negative group’, exhibited sustained 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 level of neutralizing antibodies is low.

“Our study examines neutralizing antibodies that are important in protecting against COVID-19. We found that antibodies against SARS-CoV-2 decrease in different people at different rates. This emphasizes the importance of public health and social measures in the continuous response to an outbreak. However, the presence of T-cell immunity offers hope for long-term protection, which will require further studies and time for epidemiological and clinical evidence to confirm, “said associate professor David Lye, director of the Training Office. and Infectious Disease Research, NCID, also a corresponding author of the study.

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

The findings are important as policymakers design vaccination programs and pandemic exit strategies. The rate of decrease in antibodies suggests that reinfection may occur in subsequent waves of infection. In addition, if the immunity provided through vaccinations decreases like antibodies produced naturally, then annual administration of the vaccine may be necessary to prevent future outbreaks of COVID-19. More research will be needed to clarify this as vaccine programs are implemented.