Why This Matters
Vaccines are the most effective public health tool available for protecting older adults from influenza, COVID-19, RSV, and pneumonia. But they work less reliably in people over 65 than in younger adults. The immune system changes with age in ways that reduce its ability to recognize and remember vaccine antigens, build antibody responses, and mount lasting protection. That biological gap has real clinical consequences: the populations most vulnerable to severe respiratory illness are also the least reliably protected by standard vaccine formulations.
A new study from researchers at the University of Oxford and the Max Delbrück Center for Molecular Medicine suggests a naturally occurring compound may help close part of that gap. The compound, spermidine, is found in everyday foods including wheat germ, mushrooms, and aged cheeses like parmesan and cheddar. In a pilot trial, a daily supplement improved vaccine immune responses specifically in older adults whose immune systems had not responded adequately to vaccination.
The finding is preliminary and limited to a small group. But the mechanism it illuminates and the population it targets make it worth understanding now, as annual flu and respiratory virus vaccine season approaches.
What We Know So Far
The study, led by Professor Katja Simon of the Max Delbrück Center and Associate Professor Ghada Alsaleh of Oxford's Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), was published in Aging Cell in June 2026 and received broad media coverage after a press release from the Max Delbrück Center on July 20, 2026.
The research was a double-blind, randomized, placebo-controlled pilot trial enrolling 40 healthy adults older than 65. All participants had already received three doses of a COVID-19 vaccine. Researchers gave half the group a daily oral spermidine supplement of 6 mg and the other half a placebo, continuing for 13 weeks. The treatment began approximately four weeks after participants received their third vaccine booster, timed to evaluate effects on the long-term adaptive immune memory response.
The supplement was found to be safe and well tolerated, with no adverse effects linked to treatment.
Where the Risk — and the Potential Benefit — Is Concentrated
The study's most significant finding is that spermidine did not appear to improve vaccine responses across all participants equally. It specifically benefited older adults who had not already mounted a strong antibody response to their COVID-19 vaccination.
Researchers found that vaccine non-responders in the older cohort showed a distinct biological signature: elevated markers of a process called immunosenescence, meaning their immune cells showed signs of cellular aging that reduced their ability to respond to antigens. In those individuals, spermidine reversed some of these cellular aging features and significantly enhanced spike-specific antibody secretion, memory B cell recall responses, and neutralizing antibody activity.
Participants who already responded well to their vaccine saw little change from spermidine treatment. The supplement appeared to help specifically where the immune system needed it most, according to researchers.
This pattern matters because identifying who is a vaccine non-responder in advance is not routinely done in clinical practice. Most older adults receive their annual flu or COVID booster without any measurement of whether their immune system is mounting an adequate response. The spermidine finding, if replicated in larger trials, could point toward a strategy for improving protection in a subset of older adults who are currently receiving vaccines but not gaining full benefit from them.
What Doctors and Experts Say
Professor Simon described the findings as a proof of concept for targeting immune cell senescence to improve vaccine responsiveness in older adults. In the context of the trial, she also issued a clear caution about what the findings do not yet prove.
"This study was designed as a pilot trial and involved a relatively small number of participants," Simon said in the Max Delbrück Center press release. "Larger studies will be needed to determine whether spermidine can consistently improve vaccine responses and whether similar effects are seen with other vaccines, such as those used against seasonal influenza."
The biological mechanism identified in the study involves autophagy, a cellular maintenance process in which cells break down and recycle damaged or dysfunctional components. Spermidine is known to stimulate autophagy. As people age, autophagy declines in immune cells, which is thought to contribute to their reduced responsiveness. The researchers found that spermidine supplementation increased markers of autophagic activity specifically in the B cells of vaccine non-responders, providing a plausible mechanistic explanation for the improved antibody responses observed.
What the Evidence Shows and What It Does Not
This is a pilot trial, which by design is intended to test feasibility, safety, and preliminary signal before committing to a full-scale study. The 40-participant sample is too small to draw conclusions about how broadly the benefit applies, what the correct dose is, which specific vaccines might benefit from the approach, or whether the effect persists over time.
The trial enrolled healthy older adults over 65 in a controlled research setting. People with underlying immune conditions, those taking immunosuppressive medications, or those with significant comorbidities were not included. Whether spermidine would produce similar effects in those populations is unknown.
Additionally, the trial focused specifically on COVID-19 vaccination. Professor Simon explicitly noted that it is not yet known whether similar effects would appear with influenza or other commonly administered adult vaccines.
MedicalDaily Evidence Check
- Study type: Double-blind, randomized, placebo-controlled pilot trial
- Institution: University of Oxford (NDORMS) and Max Delbrück Center for Molecular Medicine
- Published in: Aging Cell (DOI: 10.1111/acel.70545), June 2026; press release July 20, 2026
- Participants: 40 healthy adults over age 65 who had received three COVID-19 vaccine doses
- What it found: Daily 6 mg spermidine for 13 weeks improved antibody responses, memory B cell activity, and neutralizing antibody levels in vaccine non-responders; was safe and well tolerated
- What it did not prove: That spermidine improves immune response in all older adults; that results apply to influenza, RSV, pneumonia, or other vaccines; that the effect is durable beyond the study period
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What readers should know: This is a promising early finding requiring replication in much larger trials before any clinical guidance can change
Who Faces the Greatest Risk?
Vaccine efficacy declines with age for several biological reasons, including immunosenescence and the reduction of autophagy in immune cells. The older adults most likely to be vaccine non-responders include:
- People 75 and older, in whom immune aging is most advanced
- Individuals with frailty, chronic low-grade inflammation, or metabolic conditions that further impair immune function
- People with multiple comorbidities who take several medications, some of which can affect immune cell activity
- Those with prior cancer diagnoses or on immunosuppressive therapies
Spermidine levels in the body decline naturally with age, which is part of why the researchers hypothesized that supplementation might partially restore immune function in older adults.
Symptoms and Warning Signs to Watch For
Vaccine non-response in older adults is typically invisible: people receive their vaccine and assume they are protected without any way to confirm their antibody response. Warning signs that may suggest inadequate vaccine protection include:
- Breakthrough infection with a pathogen one is vaccinated against, particularly if the infection is severe
- A history of repeated serious respiratory infections despite up-to-date vaccination
- Known low antibody titers after vaccination, if tested
Most older adults are not routinely tested for antibody levels after vaccination. Anyone concerned about vaccine non-response should speak with their primary care physician about whether antibody testing is appropriate for their situation.
What You Can Do Now
- Stay current with all recommended vaccines for adults over 65, including the annual influenza vaccine, COVID-19 updated formulations, RSV vaccine (if not yet received), and pneumococcal vaccine. Completing recommended vaccination is the most effective protective step available regardless of this study's findings.
- Do not purchase spermidine supplements based on this research alone. The study used a specific 6 mg daily dose in a controlled trial setting, and commercial supplements vary widely in formulation, dose, and quality.
- If you are over 65 and concerned about vaccine effectiveness, ask your physician about whether your immune function has been assessed or whether antibody testing after vaccination is appropriate.
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Eat a diet that naturally includes spermidine-rich foods such as whole grains, mushrooms, legumes, and aged cheeses. These foods carry other established nutritional benefits, but no evidence yet exists that dietary spermidine alone is sufficient to replicate the trial's supplementation effects.
Cost and Access: What Patients Should Know
Spermidine supplements are available over the counter at health food retailers and online, but they are not regulated by the FDA as drugs and their quality, dosing accuracy, and purity vary significantly. No regulatory agency currently recommends spermidine supplementation for vaccine response improvement, and clinical guidance has not changed based on this pilot study.
Recommended adult vaccines for people over 65 are covered at no cost under Medicare Part B and most private insurance plans for influenza, COVID-19, RSV, and pneumococcal disease. There is no out-of-pocket cost barrier to the standard vaccines already proven to reduce disease severity, hospitalization, and death in older adults.
What Happens Next
The research team has signaled the need for larger follow-up trials to confirm whether spermidine can consistently improve vaccine responses, identify which older adults benefit most, determine the optimal dose, and test the approach with influenza, RSV, and other vaccines. Those trials have not yet been announced.
The study opens a broader question about whether immune senescence markers could be used to identify older adults who are vaccine non-responders before they experience a preventable infection, and whether other interventions targeting autophagy might produce similar effects.
The Bottom Line
A carefully designed pilot trial from Oxford and the Max Delbrück Center has found that a naturally occurring compound called spermidine helped improve COVID-19 vaccine immune responses in older adults whose immune systems had not responded adequately to vaccination. The effect was specific to non-responders, appears to work through a biological mechanism related to cellular maintenance, and the supplement was safe in the study population. The trial enrolled only 40 people, and much larger studies are needed before this finding changes clinical practice. For now, staying current on all recommended adult vaccines remains the most important and well-proven protective action.
