Study Identifies "Rapid-Decliners": Why Some People Lose COVID Vaccine Protection Faster

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The Hidden Group That Loses COVID Protection Fast: "Rapid-Decliners" Identified in New Study

NAGOYA, Japan — Why do some individuals remain protected by a COVID-19 vaccine for months, while others see their immunity wane quickly? A groundbreaking new study from Japan provides a crucial answer, identifying a specific group of people—dubbed "rapid-decliners"—who lose their antibody protection at an accelerated rate, even after a strong initial response.

Published in Science Translational Medicine, the research from Nagoya University tracked 2,526 individuals for 18 months, using long-term data and AI analysis to map their immune responses after vaccination and boosters. For the first time, scientists systematically classified these responses into four distinct patterns:

• Durable Responders (29%): Maintained high antibody levels over a long period.

• Rapid-Decliners (19%): Started with the highest antibody levels but experienced a rapid decline.

• Vulnerable Responders (28%): Produced few Antibodies that also declined rapidly.

• Intermediate Responders (24%): Fell in between the other categories.

The "rapid-decliner" group was the most surprising finding. Despite their powerful initial immune response, they were infected with COVID-19 sooner than other groups.

"In spite of their impressive initial immune response, they caught COVID-19 sooner than other groups, while durable responders maintained protection for longer periods," explained senior author Professor Shingo Iwami. "One-time blood tests for IgG Antibodies... couldn't detect this risk. Only by tracking changes over months did we see the pattern."

The study also pinpointed a key biomarker for breakthrough infection risk: IgA(S) Antibodies. These Antibodies serve as the first line of defense in the nose and throat. Participants who experienced infections had significantly lower blood levels of IgA(S) several weeks after vaccination. Critically, the study found a strong correlation between blood and nasal IgA(S) levels, meaning a simple blood test could potentially assess the strength of a person's mucosal immunity in the airways.

While the absolute differences in infection rates were modest, the implications for public health are significant. Identifying rapid-decliners through longitudinal monitoring could help tailor personalized vaccination strategies, determining who might need booster shots sooner.

"This is the first time we've been able to clearly group how people respond to COVID-19 vaccines," Professor Iwami noted. "Identifying the rapid-decliner pattern is especially important—it helps explain why some people may need boosters sooner than others."

The research paves the way for more effective and individualized vaccine rollout programs, though the authors note that more research is needed to understand the underlying biological mechanisms behind these response patterns.

About the Study:
The research was conducted by scientists at Nagoya University's Graduate School of Science and published in Science Translational Medicine. The study prospectively followed 2,526 participants, measuring their antibody levels over 18 months to characterize dynamic immune response patterns to COVID-19 vaccination.