Wednesday, September 17, 2025

Scientists identify four ways our bodies respond to COVID-19 vaccines

A Japanese study reveals a group who lose vaccine protection faster than others—even if they start with stronger antibody levels.

Nagoya University

Tracking COVID-19 vaccine responses — image:
How COVID-19 vaccine responses change across individuals
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Credit: Kyoko Kojima

Two healthcare workers get COVID-19 vaccinations on the same day. Both show strong antibody responses initially, but six months later one stays healthy while the other contracts the virus. A new study published in Science Translational Medicine could help explain this difference.

Researchers tracked individuals’ antibody levels after vaccinations and identified four distinct patterns of immune response after the first booster vaccination. Notably, the group that started with the highest antibody levels but experienced a faster decline were infected earlier. People with lower blood levels of IgA(S) antibodies, which protect the nose and throat, were also at higher risk. The findings suggest that monitoring how antibody levels change over time could assist in identifying individuals at greater risk of infection.

Led by scientists from Nagoya University in Japan, the research team measured antibody levels in 2,526 people over 18 months to see how vaccine responses changed between the first vaccination and later booster shots. They developed a mathematical classification system for COVID-19 vaccine responses using long-term tracking and AI-based computer analysis, becoming the first to systematically identify and characterize the “rapid-decliner” group.

The researchers found that immune responses fell into four clear patterns: some people maintained high antibody levels over time (durable responders), others started with strong levels but lost them quickly (rapid-decliners), a third group produced few antibodies that also declined rapidly (vulnerable responders), and the rest fell in between (intermediate responders).

Immunity that peaks early and then drops

According to Shingo Iwami, senior author and professor at Nagoya University’s Graduate School of Science, the results for the rapid-decliner group were surprising. “In spite of their impressive initial immune response, they caught COVID-19 sooner than other groups, while durable responders maintained protection for longer periods. One-time blood tests for IgG antibodies, the antibody type we used for classification, couldn't detect this risk. Only by tracking changes over months did we see the pattern,” he explained.

A breakthrough or subsequent infection refers to infections that occur after vaccination because the virus overcomes the immune protection that vaccines provide. The researchers found that people whose antibodies declined faster, either because they started low or dropped quickly (vulnerable responders and rapid-decliners), were slightly more likely to get breakthrough infections earlier.

After booster vaccinations, 29% of participants fell into the durable responder category, 28% were vulnerable responders, and 19% were rapid-decliners. The remaining participants showed intermediate patterns. The differences in breakthrough infection rates between groups were modest—5.2% for durable responders and 6% for vulnerable and rapid-decliners.

Breakthrough infections linked to IgA(S) antibody levels

The study also revealed that participants who experienced breakthrough infections had lower levels of IgA(S) antibodies in their blood several weeks after vaccination. These antibodies protect the nose and throat and are our first line of defense against respiratory viruses.

Importantly, the researchers found a strong correlation between blood IgA(S) levels and nasal IgA(S) levels, suggesting that blood tests can reliably indicate the strength of immune protection in airways. As a result, measuring blood IgA(S) levels after vaccination may help identify individuals at higher risk for breakthrough infection, especially among vulnerable groups.

While these results provide a foundation for future research, Professor Iwami emphasized the importance of identifying the underlying biological mechanisms responsible for the rapid decline in antibody levels in order to develop more effective vaccination strategies. Previous research points to factors such as age, genetic variation, vaccine-specific characteristics, and environmental influences, including sleep habits, stress levels, and medications being taken at the same time.

“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. This could potentially contribute to better, more personalized vaccination strategies. However, whether antibody testing can be used widely depends on cost, accuracy, and if the benefits are worthwhile compared to current strategies. More research is needed to understand its full potential.”

Journal

Science Translational Medicine

DOI

10.1126/scitranslmed.adv4214

Article Title

Longitudinal antibody titers measured after COVID-19 mRNA vaccination can identify individuals at risk for subsequent infection

Article Publication Date

17-Sep-2025

Researchers tracked dynamics of antibody levels between initial COVID-19 vaccinations and booster shots to understand why vaccine protection varies between individuals.

Blood samples taken from 2,526 participants over 18 months were analyzed using mathematical models and machine learning to classify antibody response patterns.

Four antibody response patterns were identified, with breakthrough infections linked to lower IgA(S) antibody levels.

Predicting the risk of subsequent infection after COVID-19 vaccination

Credit
©Kana Ariga

Major report tackles Covid’s cardiovascular crisis head-on

University of East Anglia

Regular Covid vaccinations should continue worldwide to reduce cardiac risks associated with the virus - according to new research from the University of East Anglia.

A major report published today sets out ways of tackling the ‘profound and lasting impact’ of Covid and long Covid on cardiovascular health.

It makes recommendations for diagnosing, treating and preventing serious heart and blood vessel complications linked to the virus.

As well as continuing vaccination programmes, the report recommends structured cardiac rehabilitation - to prevent long-term problems after infection and boost long Covid recovery.

The clinical consensus statement is authored by a group of experts from across Europe, led by Prof Vassilios Vassiliou from UEA and the Norfolk and Norwich University Hospital on behalf of the European Society of Cardiology (ESC).

Millions suffering

Prof Vassiliou, from UEA’s Norwich Medical School, said: “The Covid pandemic has had a profound and lasting impact on our health, with complications emerging during acute illness and recovery.

“Millions of people around the world are suffering with serious cardiovascular problems caused by Covid infection and long Covid.

“A lack of clear evidence-based guidance on how to reduce this suffering and prevent further harm means that patients are not receiving the care they need, and some are turning to unproven or unsafe treatments.

“We wanted to change that.”

Almost one billion people are known to have been infected with Covid worldwide, although the true number is believed to be far higher.

Research shows that Covid patients, especially those who needed hospital treatment, have a higher risk of cardiovascular disease, including heart attack, stroke and death from cardiovascular disease.

Around 100 million people are currently living with long Covid, and about five per cent of these have cardiac long Covid, with symptoms including angina (chest pain), breathlessness, arrhythmia (abnormal heart rhythm), heart failure, fatigue and dizziness.

Long Covid can also lead to autonomic dysfunction where the nerves that normally control heart rate, breathing and body temperature do not work properly.

How the research happened

The team reviewed all existing research on the virus and cardiovascular disease, including the effects of an acute infection, long Covid and Covid vaccination.

They used this research to agree a set of recommendations for how to treat or prevent the damaging cardiovascular effects of Covid.

The report includes advice to continue vaccinating against Covid-19, as people who are fully vaccinated are far less likely to suffer cardiac complications or long Covid, even if they come down with the virus.

It also sets out how to diagnose and treat the symptoms brought on by Covid, such as shortness of breath, chest pain and fainting.

Cardiac rehabilitation vital

In particular, the paper recommends structured cardiac rehabilitation programmes, including specialised physiotherapy, to prevent longer term problems from developing following infection and to aid recovery from long Covid.

Prof Vassiliou said: “Covid doesn’t just affect the lungs. It can also damage the heart and blood vessels, both during the acute infection and for months afterward. This means chest pain, breathlessness, palpitations, or fatigue may be signs of cardiac long Covid.

“If you already have heart disease, Covid raises your risk of serious complications both immediately and long after infection. In both cases, rehabilitation can protect your heart and support recovery.

“Our report provides unified, practical recommendations for prevention, rehabilitation, and long-term care, while also identifying critical research gaps to ensure strategies continue to evolve with emerging evidence.”

Finally, the experts call for equal access to cardiac rehabilitation programmes, especially for people living in rural locations.

“At present, the capacity of rehabilitation services across much of Europe is insufficient to accommodate both conventional cardiac patients and those with cardiac long Covid,” said Prof Vassiliou.

“There are also significant regional variations. Targeted financial investment and resource allocation are therefore required to expand service capacity and ensure equitable access.

“Unfortunately, even now, cardiac long Covid continues to affect the quality of life for many patients. We need to ensure patients have equitable access to rehabilitation services, support primary prevention through vaccination and lifestyle programmes, and fund research into long Covid and cardiovascular outcomes.

“Health systems must be prepared for the ongoing burden, not just the acute infection.”

‘Cardiovascular Disease Prevention and Management in COVID-19. A Clinical Consensus Statement of the European Association of Preventive Cardiology, the European Association of Cardiovascular Imaging, the Association of Cardiovascular Nursing & Allied Professions, the European Association of Percutaneous Cardiovascular Interventions, and the Heart Failure Association of the ESC’ is published in the European Journal of Preventive Cardiology