Continuing from my post on probiotics and respiratory viruses, I want to review some trials that studied how probiotics can augment the effects of a flu shot.
When the seasonal flu vaccine closely matches circulating influenza viruses, effectiveness against catching the flu ranges between 70-90% in healthy adults. Unfortunately, unlike wine, these statistics do not improve with age.
The preventive effect typically declines to 30-40% in elderly patients living in institutions. (1) Even so, it is still 50-60% effective in preventing hospitalization and pneumonia, and 80% effective in preventing death in this age group. (2) For those over 60 living alone, it is about 58% effective at preventing the flu, although this percentage declines after the age of 70.
The reason why is due to a decline in antibody formation. This phenomenon is called immunosenescence. It is an obvious cause of concern for medical care givers trying to prevent premature death in the elderly from flu viruses.
The hunt has been on for some time to discover effective flu shot enhancing substances (adjuvants) for this population group. One such adjuvant under study are probiotics. A number of placebo-controlled trials have shown that probiotic administration can increase the body’s response to a number of different vaccines.
A 1994 study found that healthy volunteers who received lactobacillus developed higher levels of antibodies in response to a Salmonella typhi oral vaccine than those who received a placebo. (3) These results were duplicated in another randomized, placebo-controlled trial published in 2000. (4)
Infants receiving Lactobacillus casei had higher rates of antibody formation to an oral rotavirus vaccine than infants receiving just the vaccine and a placebo. (5) Rotavirus is the most common cause of severe diarrhea in infants and children.
Another study found that volunteers who consumed a probiotic dairy product before receiving a polio-booster shot developed higher levels of antibodies than their placebo cohorts. (6)
In a trial conducted in newborns, supplementing with a probiotic formula containing Bifidobacterium longus and Lactobacillus rhamnosus increased antibodies to hepatitis B vaccination. (7)
When it comes to the flu vaccine, studies in adults and the elderly have also shown enhanced antibody formation when administered alongside probiotics.
In one study conducted in Chile, adults over 70 years of age were given a nutritional formula that contained both a probiotic and a prebiotic for four months prior to receiving a flu shot. (8) Elders supplemented with this formula experienced increased natural killer cell activity and no declines in T cell immunity after immunization in contrast to the vaccinated-placebo group. The elders receiving the probiotic/prebiotic formula also experienced fewer instances of the flu than the placebo group.
In another study, this time conducted in France, feeding a probiotic dairy drink containing Lactobacillus casei (paracasei) to nursing-home patients over the course of two flu seasons resulted in significant increases in influenza antibodies. (9)
In the second, and larger arm of this same study, not only were antibodies higher during the time the probiotic product was consumed, the effects were still noticeable five months after vaccination and three months after the probiotics were discontinued.
A Japanese study conducted during the flu season that ran between November 1, 2004 and March 31, 2005 found significantly higher natural killer cell and white blood cell immune activity in elderly patients who were supplemented with Bifidobacterium longum after vaccination. (10)
Between March 22nd and March 23rd, 2005, a flu outbreak hit the nursing home where this study was conducted. Although patients had received a flu shot early in the season, flu was confirmed in five patients in the placebo group. None in the probiotic group came down with it, however.
A fever outbreak was also noted during the study period. A total of eight patients in the placebo group developed a fever–five from the flu and two from an unknown origin–but only two subjects in the bifidobacteria group developed any fever.
The necessity for antibiotics was also lower in the probiotic group. Only two subjects in this group were prescribed antibiotics during the study period in contrast to seven in the placebo group.
One other fascinating finding from this Japanese trial was the increase of hematopoiesis in the group who received bifidobacteria. Hematopoiesis is the development of red blood cells. Failure to form red blood cells is a common cause of anemia in older people.
This finding is astonishing to me. This suggests that gut flora also control the production and health of red blood cells. These critters never cease to amaze me!
A 2007 Spanish study also showed increases in resistance to the flu. (11) This double-blind, placebo-controlled trial was conducted in a non-elderly, adult population. Lactobacillus fermentum was the strain tested here. Probiotics were administered two weeks before and two weeks after the flu vaccine was administered.
The treatment group experienced higher natural killer cell and T-helper cell activity. Increased antibodies to influenza were also noted along with lower rates of flu infection a full five months after vaccination.
In the United States, a small pilot study showed similar effects when lactobacillus and inulin were administered to a treatment group right after immunization with a live attenuated flu vaccine. (12) However, of the three viral strains, only antibodies to the H3N2 strain were significantly elevated in the probiotic group as compared to the placebo cohort.
One big problem I have with this study is that the placebo capsule contained inulin. This would increase bifidobacteria colonies in the control group. While great for the placebo group, this is not the way to design a placebo or compare levels of antibody production between groups.
So what’s the take-home message here?
Well, if you want to increase the effectiveness of the flu vaccine and likely boost your immune system, taking probiotics appears to be quite effective. This is especially true for those over 60 years of age whose immune systems are less able to form antibodies to a flu shot at levels sufficient enough to protect them completely throughout an entire season.