Help flu shots stick with prebiotics and probiotics?

The Bottom Line

  • The flu, and the complications associated with it, can be dangerous for older adults. The flu vaccine is the best protection available. 
  • Prebiotic or probiotic supplements taken before getting the flu shot could improve its effectiveness. 
  • Supplementation may work best in healthy older adults who take the supplements over a longer period. 

The dreaded flu season is in full swing!

Getting influenza, or the “flu”, is a miserable experience for anyone. Sudden fever, muscle aches, chills (1;2), cough, nasal congestion, and a sore throat can make you feel like you’ve been hit by a truck (2). Luckily, for many the flu will resolve on its own. But for some it can lead to serious complications (1;2), including inflammation of the heart or brain, pneumonia, or even death (1). Older adults (1), people living in nursing homes or long-term care, or people with weakened immune systems or certain chronic health conditions are especially at risk for these complications (2).

Regardless of the match between the flu vaccine and circulating flu viruses in any given year, the flu vaccine is the single best way to protect yourself against the flu (1;3;4). Among the general population, the flu shot can reduce flu risk by 40% to 60%, which helps prevent thousands of flu-related hospitalizations annually (5). Age also plays a role in determining the effectiveness of the flu shot. For example, while the vaccine reduces the likelihood of getting the flu by up to 90% in children, adolescents, and young adults, among older adults the risk of getting the flu is reduced by 30% to 40% (1;6).

But, what if there was a simple way to boost the effectiveness of the flu vaccine among older adults? Recent research explored whether prebiotic and probiotic supplementation could do just that (1). Probiotics—also referred to as “good” bacteria—are live bacteria that support overall health. Prebiotics, on the other hand, are substances that promote the growth of these beneficial bacteria (1;7). Both are found in food—oats, beans, and bananas are prebiotic foods, while kimchi, sauerkraut, and kombucha tea are probiotic foods (7).

So, does supplementation with these immune-boosters enhance the protection offered by the flu vaccine?

What the research tells us

systematic review and meta-analysis found that taking prebiotic or probiotic supplements before a flu shot can improve the effectiveness of the vaccine. This review evaluated people who had taken probiotic supplements alone, prebiotics and probiotics together, or prebiotic supplements mixed with other substances like vitamins, minerals, oils, or fermented milk. Supplements were taken for at least two weeks, and up to 28 weeks before receiving flu vaccines designed to protect against the H1N1, H3N2, and B flu strains. Overall, people who took prebiotics or probiotics before receiving their flu shot had increased protection from certain strains of the flu compared to those who received a placebo. Specifically, healthy older adults who took the supplements over longer periods of time seemed to benefit the most.

These results are promising, but future research will be useful in determining the best combination of supplements, dose at which they need to be taken, and for how long in order to achieve the most benefit and to help further support the findings seen here (1). Clearer conclusions around side effects and safety are also needed.

So there you have it! The flu shot remains the best way to protect yourself against the flu, but supplementation with prebiotics or probiotics before getting the vaccine may be one way to boost its protective effects (1;8).

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Author Details


  1. Lei WT, Shih PC, Liu SJ, et al. Effects of probiotics and prebiotics on immune response to influenza vaccination in adults: A systematic review and meta-analysis of randomized controlled trials. Nutrients. 2017; 9(11):E1175. doi: 10.3390/nu9111175. 
  2. Mayo Clinic. Influenza (flu). [Internet] 2022. [cited February 2023]. Available from
  3. Centers for Disease Control and Prevention. Prevention and control of influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2011. Morb Mortal Weekly Rep. 2011; 60:1128-1132.
  4. World Health Organization. Influenza vaccine response during the start of a pandemic report of a WHO informal consultation held in Geneva, Switzerland 29 June – 1 July 2015. Wkly Epidemiol Rec. 2016; 91(23):302-303.
  5. Centers for Disease Control and Prevention. How well flu vaccines work. [Internet] 2023. [cited February 2023]. Available from 
  6. Brydak LB, Machala M, Mysliwska J, et al. Immune response to influenza vaccination in an elderly population. J Clin Immunol. 2003; 23:214-222. 
  7. Lewis, S. Probiotics and prebiotics: What’s the difference? [Internet] 2023. [cited February 2023]. Available from
  8. Vedhara K, Royal S, Sunger K, et al. Effects of non-pharmacological interventions as vaccine adjuvants in humans: A systematic review and network meta-analysis. Health Psychol Rev. 2021; 15(2):245-271. doi: 10.1080/17437199.2020.1854050.

DISCLAIMER: These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (

Many of our Blog Posts were written before the COVID-19 pandemic and thus do not necessarily reflect the latest public health recommendations. While the content of new and old blogs identify activities that support optimal aging, it is important to defer to the most current public health recommendations. Some of the activities suggested within these blogs may need to be modified or avoided altogether to comply with changing public health recommendations. To view the latest updates from the Public Health Agency of Canada, please visit their website.