Viruses that cause respiratory tract infections are found in various virus families, which differ in virulence and utilize variable strategies to infect the host cells and to evade the host immune system. Among non-pharmacological solutions for the management of these respiratory tract infections, probiotics have been proposed as an adequate solution. Indeed, probiotics have been shown to modulate immune system function and their role in reducing the risk and the course of these infections has been investigated extensively within the past decade.

This review was focused on the immunomodulatory mechanism of probiotics. Based on in vitro, in vivo authors highlighted the ability of probiotics to inhibit viral replication of different viruses involved in respiratory tract infections and to stimulate the antiviral response in different. These observations have been confirmed in different clinical studies in children, adults and elderly presenting respiratory tract infections without specific etiology.

In conclusion, despite some evidence of the efficacy of particular probiotic strains in the management of respiratory tract infections, additional clinical evidences are required to conclude on the efficacy of probiotics supplementation in the management of infections of viral etiology.

Lehtoranta L, Latvala S, Lehtinen MJ. Role of Probiotics in Stimulating the Immune System in Viral Respiratory Tract Infections: A Narrative Review. Nutrients. 2020 Oct 16;12(10):E3163. doi: 10.3390/nu12103163. PMID: 33081138.