The working hypothesis is that the administration of a Lactobacillus strain improves the immune response in the elderly population, improving the immune response to a possible COVID-19 infection. The strain would act as an adjuvant that contributes to developing an effective response against the virus, and therefore there are fewer infectious symptoms due to this virus or, if it appears, it occurs in a milder way among the subjects who take the probiotic strain. Also,the investigators hypothesizes that the administration of the Lactobacillus may improve the immune response generated by the Covid-19 vaccine in this elderly population.
The objective of this trial is to evaluate the effect of the consumption of a probiotic strain on the incidence and severity of COVID-19 in elderly population living in a nursing home. In addition, it will be evaluated if the probiotic strain have some effect on the immune response generated by the Covid-19 vaccine inthis population.