The goal of this randomised controlled trial is to determine the effect of consuming a multistrain probiotic OMNi-BiOTiC® Active to shorten the incidence and duration of acute upper respiratory tract infections (URTIs) in older people. The main questions it aims to answer is:

• Is the multistrain probiotic OMNi-BiOTiC® Active effective in reducing the incidence of URTIs in older people?
• Is the multistrain probiotic OMNi-BiOTiC® Active effective in reducing the duration of URTIs in older people?
• Is the multistrain probiotic OMNiBiOTiC® Active effective in changing selected immunological blood parameters in older people? Researchers will compare the probiotic group and the placebo group to see if the incidence or duration of URTIs are significant among the groups.

Inclusion Criteria:

• 65 years or older at the signing of the written consent form
• ability of participant to eat independently
• ability of participant to adhere to all procedures of the clinical study

Exclusion Criteria:

• participants experienced an exacerbation of an existing chronic disease
• participants experienced an exacerbation of metabolic diseases,
• participants with mental incapacity to understand instructions
• participants were prescribed long-term usage of antibiotics.
• participants that changed their eating habits or consumed any probiotics 14 days
• participants with markedly abnormal results of blood tests were excluded.