Does obesity make vaccines less effective?
New research suggests that obesity disrupts the immune machinery vaccines rely on, but immune cells in the lungs can compensate.
- 16 April 2026
- 5 min read
- by Priya Joi
At a glance
- Obesity affects the way vaccines trigger antibody production, but a University of Missouri study found that T cells stationed deep in the airways compensated by providing back-up protection against infection.
- The study is one of the first to test how body weight affects the response to a bacterial vaccine, using a next-generation candidate against Pseudomonas aeruginosa.
- The findings suggest that vaccines designed to target these tissue-resident defences, rather than relying on antibodies alone, could better serve the more than one billion people living with obesity worldwide.
For the more than one billion people worldwide living with obesity, vaccines against influenza, hepatitis B and rabies consistently generate weaker antibody responses.
Obesity has also been linked to chronic inflammation that disrupts how immune cells coordinate their defence, while also compromising lung function, leaving people more vulnerable to respiratory infections and less protected by the vaccines meant to prevent them.
The finding points to a clear conclusion: vaccines need to be designed differently if they are going to work reliably for people with obesity.
New research published in The Journal of Immunology has furthered this understanding of how vaccines work in people with obesity.
In one of the first studies to examine how obesity affects immune responses to a bacterial vaccine, scientists found that, while antibody production was impaired, a different arm of the immune system (cells hidden deep in lung tissue) stepped in as back-up.
The team, led by Professor Wendy Picking at the University of Missouri, says the finding points to a clear conclusion: vaccines need to be designed differently if they are going to work reliably for people with obesity, targeting these lung-based defences rather than relying on antibody production alone.
How did the researchers test the effects of obesity on immunity?
The new study tested a next-generation vaccine against Pseudomonas aeruginosa, a leading cause of severe pneumonia.
People with obesity face a significantly higher risk from this bacterium, and rising antibiotic resistance is making those infections increasingly difficult to treat. Yet until this study, no research had examined how obesity affects immune responses to vaccines targeting gram-negative bacteria like Pseudomonas.
The researchers tested this on mice fed a high-fat diet (with 60% of calories from fat) compared with mice on a low-fat diet. The mice strains used were selected for their genetic similarity and propensity to dietary-induced obesity.
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All groups were given the same experimental vaccine, called L-PaF/ME/BECC, a protein subunit formulation developed specifically to generate strong immune responses against P aeruginosa.
All three groups showed an immune response to the vaccine, but the quality and durability of that response differed dramatically depending on the animals’ diet.
How does obesity affect immunity?
In healthy mice, the vaccine triggered robust antibody production. In obese mice, antibody levels were significantly lower and declined more rapidly over time.
To understand why, the researchers investigated the cellular machinery behind antibody production. The answer pointed to a structure called the germinal centre.
Germinal centres are temporary microenvironments in the immune system where B cells mature and produce high-quality antibodies. They are also where long-term immune memory is forged.
In the obese mice, germinal centre formation was severely compromised. B cells and T helper cells (the specialist cells that help B cells mature and produce antibodies) didn’t response strongly enough vaccination because the communication signals within these immune hubs was disrupted.
Lung-resident memory B cells, which also contribute to longlasting immune protection, were also impaired. This combination of defects helps explain why standard vaccine designs that rely on high antibody production tend to perform poorly in people with obesity.
Hidden defences
However, as the researchers found, even with these antibody deficiencies, the obese mice were still somewhat protected against infection.
When infected with P aeruginosa, all vaccinated groups, including those on the high-fat diet, showed substantially lower bacterial loads in their lungs compared to unvaccinated mice.
The mechanism behind this protection was not antibodies. It was memory T cells that permanently live in lung tissue and don’t circulate in the bloodstream. Unlike antibodies, which are produced elsewhere and travel to sites of infection, these cells are already present at the site where pathogens like P aeruginosa enter the body.
The vaccine generated robust populations of these resident T cells even in obese mice, compensating for the weakened antibody response.
To confirm this finding, the researchers used a drug that blocks T cells from leaving lymph nodes and entering circulation. In mice treated with this drug, the lung-resident T cells remained active and early protection against infection was maintained, demonstrating that it was the tissue-resident population, not circulating T cells, that was doing the work.
Can we design vaccines for obese populations?
The findings from this study indicate that vaccines that additionally promote tissue-resident immunity in the lungs may offer stronger, more durable protection in people with obesity.
Rather than relying exclusively on antibody levels as a marker of success, the team suggest vaccine researchers and developers could prioritise strategies that build this local line of defence directly at the point of entry for respiratory pathogens.
Next steps include identifying the specific molecular signals that activate these lung-resident T cells even in the presence of the chronic inflammation that accompanies obesity.
If researchers can identify what triggers that response, it opens the door to vaccine formulations deliberately designed to work with rather than against the immune systems of people with obesity.
