In many countries, influenza vaccination is recommended for older patients, but the immune response is weaker than for younger people.

The aim of two multicenter, randomized, double-blind, controlled trials was to assess the effect of daily intake of a fermented milk product containing probiotics on the severity of the immune response after administration of the influenza vaccine to healthy volunteers over the age of 70.

The above studies were conducted over two seasons in which study participants were vaccinated against influenza (pilot study 2005-2006 and confirmatory study 2006-2007). Eighty-six and 222 healthy elderly volunteers received either a fermented milk product containing the Lactobacillus casei probiotic strain DN-114 001 (Actimel, company Danone), or an unfermented dairy product without probiotic (control group) twice a year. one day for 7 weeks (pilot study) or 13 weeks (confirmatory study). Vaccination against influenza was carried out after 4 weeks of ingestion of the product to be tested. The mean geometric titer of the antibodies against the three strains of the virus contained in the vaccine (H1N1, H3N2 and B) was determined several times at certain intervals after vaccination using the RTGA test (hemagglutination inhibition test).

According to the results of a pilot study, influenza-specific antibody titers increased after vaccination and were higher in the dairy group with probiotics than in the control group. Similar results were obtained in the confirmatory study - influenza B antibody titers were significantly higher in the probiotic group at 3, 6 and 9 weeks after vaccination compared to the control group (p = 0.020) (all the titles were determined according to the consumption of the products studied).

Statistically significant differences between groups in the frequency of seroconversion during analysis in patients to be treated were noted 5 months after vaccination. Similar results were observed for the geometric mean titers of antibodies against strains of groups H3N2 and H1N1 viruses, thus confirming the results of a pilot study.

Thus, these studies have shown that the daily consumption of a fermented milk product containing the Lactobacillus casei DN-114001 probiotic strain improves the specific antibody response to the introduction of influenza vaccine in people over 70 years of age and therefore may be beneficial for the health of a given patient population.