Why do some people remain protected after vaccination while others quickly lose immunity and get infected? A new study from Japan provides crucial insights into this puzzle.
Researchers from Nagoya University tracked the antibody levels of 2,526 individuals for 18 months, from their first vaccination through booster shots. Using long-term data and AI analysis, they became the first to systematically classify vaccine responses into four clear patterns:
Durable Responders: Maintained high antibody levels over time.
Rapid-Decliners: Started with the strongest antibody levels but experienced a rapid decline.
Vulnerable Responders: Produced few antibodies that also declined rapidly.
Intermediate Responders: Fell between the other categories.
The "rapid-decliner" group was a key discovery. Despite their powerful initial immune response, this group was infected with COVID-19 sooner than others. "One-time blood tests... couldn't detect this risk. Only by tracking changes over months did we see the pattern," explained senior author Professor Shingo Iwami.
The study also revealed a critical link between breakthrough infections and IgA(S) antibodies, which serve as the first line of defense in the nose and throat. Individuals who experienced infections had significantly lower blood levels of these antibodies after vaccination. The research confirmed a strong correlation between blood and nasal IgA(S) levels, meaning a simple blood test could potentially assess airway immunity.
While the differences in infection rates between the groups were modest, the study lays the foundation for more personalized vaccination strategies. Identifying "rapid-decliners" could help determine who might benefit from earlier booster shots. However, Professor Iwami emphasized that more research is needed to understand the biological mechanisms behind these patterns before widespread antibody testing can be implemented.