Researchers flag probiotics’ potential to enhance vaccine efficacy

01 Jun 2021 --- A study review has revealed the gut microbiota can influence immune responses to vaccinations, suggesting probiotics could be potentially attractive interventions to improve vaccine efficacy.

“There is strong evidence from animal models and increasing evidence from clinical studies that this is the case, but further work is needed,” lead author Professor David Lynn tells NutritionInsight. Lynn is an EMBL Australia group leader based at the South Australian Health and Medical Research Institute.

He highlights pro-, pre- and synbiotics appear promising due to their safety, cost-effectiveness and scalability. They have also shown effectiveness in specific interventions, such as in infants to prevent diseases such as necrotizing enterocolitis, acute diarrhea and sepsis.

Amid the pandemic, the need for effective vaccines to induce long-lasting immunity has “never been more apparent,” the study authors highlight. For reasons still poorly understood, vaccine immune responses vary greatly between different individuals and different populations.

Furthermore, vaccine immunogenicity is frequently suboptimal in populations at most risk from infectious disease, including infants, the elderly, and those living in low-income and middle-income countries. 

Personalizing probiotics
Vaccine protection is induced by B cells that produce antigen-specific antibodies. T cells also help mediate the protection caused by some vaccines.

“Our study found increasing evidence that gut microbiota as a crucial factor modulating B and T cell immune responses to vaccinations,” says co-author Saoirse Benson, Flinders University PhD candidate.

Potential mechanisms by which the microbiota could modulate vaccine immunogenicity and efficacy.“A better understanding of how the microbiota regulates these vaccine responses may also inform the use of more tailored population-specific adjuvants to enhance responses to vaccinations,” she explains.

For example, the study emphasizes some probiotic strains have a disproportionately beneficial impact on vaccine responses and could therefore also be used to screen for more personalized probiotics depending on an individual’s microbiota.

Innova Market Insights predicted the personalization trend would make its mark on the nutrition industry in its “Tailored To Fit” top F&B trend this year. 

Incomplete understanding?
The Flinders University study review highlights that research on probiotics’ impact on vaccine responses has been “significantly underpowered.” 

Although some studies indicate scant evidence of a probiotics-vaccine efficacy link, the current study’s authors flag several limitations, including small sample sizes differences in the probiotic strains investigated, their purity and viability, and the timing, duration and dose of administration. 

“Perhaps more importantly, none of these trials specifically recruited participants with a disrupted microbiota, for example, those exposed to antibiotics,” notes the study.

Low evidence was also suggested in studies conducted in elderly populations. “However, the number of participants was small and these studies mostly used probiotics containing Lactobacillus strains, which are not commonly found in the adult gut,” the authors outline.

Limited effect of probiotics on healthy people
Despite probiotics’ potential, several limitations to the probiotics-vaccine efficacy link remain. Overall, most trials remain limited in size, warranting further research with larger trials. 

From left to right: Study co-authors Saoirse Benson and Dr. Miriam Lynn with Prof. David Lynn (Credit: Flinders University).“Furthermore, it is highly unlikely that administering probiotics to already well-colonized, healthy individuals would have a significant effect on the immune response to vaccination,” states Lynn.  

“It may be better to conduct trials in individuals with a disrupted microbiota, for example, infants exposed to antibiotics.”

Push for vaccine research from COVID-19
The coronavirus pandemic has pushed for an improved understanding on vaccine efficacy. “All the COVID-19 vaccines to date induce very robust immune responses,” notes Lynn. 

“However, microbiota-targeted interventions may be beneficial in certain populations to further enhance responses such as in the elderly. This has not been assessed yet.” 

NutritionInsight previously reported on early indications of probiotics’ potential in fighting viral infections. Industry players such as Lallemand and Probi have previously looked to probiotics to serve as a vaccine vehicle. Throughout 2020, ADM probiotic strains were also trialed for COVID-19 patients in hospital care.

By Anni Schleicher