New study finds nearly half of vaccine recipients may lose antibodies within nine months after booster

A new analysis of antibody data from 2,526 adults in Fukushima, Japan, found that while the Pfizer-BioNTech and Moderna vaccines likely prevented severe illness, immune protection waned more quickly than previously thought. Researchers said roughly half of participants experienced a substantial decline in antibodies within nine months after a booster.

Over an 18-month follow-up, researchers identified four patterns of immune response after the booster: durable responders, rapid decliners, vulnerable responders, and intermediate responders. Durable responders accounted for about 19 percent of participants, while rapid decliners made up about 19 percent and vulnerable responders about 28 percent; the remainder were intermediate. Nearly half of participants fell into the rapid-decliner or vulnerable categories. Covid-19 infection rates were higher in the rapid-decliner and vulnerable groups: 6 percent vs 5.2 percent in durable responders, a relative difference of about 14 percent.

Within three months of a booster, about one in five in the rapid-decliner and vulnerable groups had contracted the virus, rising to about half by six months, compared with roughly one in five among durable responders. The Nagoya University team said these groups did not maintain high antibody levels for long after boosting and warned they were at higher risk for infection following vaccination. They suggested that administering additional booster doses or antibody therapy may be warranted, but cautioned that the reasons for weaker responses are not yet clear.

These findings come as part of a broader debate about vaccine impact and booster strategies. A 2022 Imperial College London study estimated nearly 20 million lives were saved in the first year of vaccine rollout, largely in high-income nations. Across the globe, roughly 13.6 billion doses have been administered, with about 70 percent of people receiving at least one dose.

Some researchers have described a so-called post-vaccination syndrome in connection with mRNA vaccines, noting symptoms such as brain fog, dizziness, tinnitus, and exercise intolerance. Some cases have shown changes in immune cells and traces of coronavirus proteins in the blood years after vaccination. These findings are preliminary, not peer-reviewed, and the authors say the results are still a work in progress.

World Health Organization figures widely cited by vaccine supporters indicate that jabs prevented about 14.4 million deaths in the first year of rollout, with some estimates approaching 20 million. The new study does not dispute the vaccines’ broad benefits but underscores the need for ongoing research into durability and potential tailored booster approaches for individuals at higher risk of waning immunity.

Health officials cautioned that the findings should inform ongoing vaccination policy rather than seed hesitancy. Experts say the results highlight the potential value of individualized vaccination strategies and continued monitoring of immune responses as the pandemic era evolves.