Repair-like response to flu vaccine weakens in older mice
After flu vaccination with an immune-boosting ingredient, female mice aged 18–24 months had a weaker repair-like immune response than mice aged 6–8 weeks.
Our read
Interventions- Studied:
- Experiments in young and aged female mice, against young mice receiving the same vaccine
- What changed:
- Muscle macrophage and regulatory T-cell counts were 3-fold lower in aged than young mice after adjuvanted flu vaccination
- The catch:
- Immune-cell counts and markers stood in for direct measurements of muscle repair
- Stake:
- An author holds shares in argenx.
- In the record:
- One of 4 papers on quadrivalent inactivated influenza vaccine on record: none yet with results in people, 1 in animals.
Editor of record: Boris Djordjevic · AgingResearch.News
Female BALBc/J mice aged 6–8 weeks and 18–24 months received an injected influenza vaccine with AddaVax, a squalene-based immune-boosting ingredient, in an animal experiment. The injection triggered a repair-like immune response in muscle. Within four days, macrophages—immune cells that engulf material—increased in muscle and nearby lymph nodes.
Vaccination also increased levels of one antibody type and, after influenza infection, certain immune signaling proteins in the lungs—a pattern known as a type 2 immune response. Older mice had weaker macrophage and type 2 responses. Transferring macrophages grown from young mice’s bone marrow into older mice restored a type 2 bias. The transferred cells took up vaccine material and moved to lymph nodes. But the transfer did not improve protection against an influenza virus that did not match the vaccine.
Why it matters
Muscle damage and repair may help shape how injected vaccines work. Understanding that connection could clarify how age-related changes in muscle repair influence vaccine effectiveness.
Caveats
The experiments used female mice from one strain; the findings do not show whether the same response occurs in male mice or people.
The paper
Icahn School of Medicine at Mount Sinai
NPJ Vaccines, Jul 4, 2026, Open access
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