Efficacy Of Om-85 In Recurrent Respiratory Tract Infections.

Background In older patients, prevention of acute respiratory tract infections (RTIs) is challenging. Experimental studies have consistently underlined an immune-potentiating effect of the bacterial lysates product OM85, on both cellular and humoral responses. Objective This work aimed to assess the potential efficacy of OM-85 for RTIs' prevention in older individuals. Methods This explorative longitudinal study included 24 patients aged 65 years or older recruited in the GeroCovid Observational Study- home and outpatient care cohort. For the study purposes, we included 8 patients treated with OM-85 from December 2020 to June 2021 (group A), and a control group of 16 patients, matched for sex and age, who did not receive bacterial lysates (group B). RTIs were recorded from the participants' medical documentation in an e-registry from March 2020 to December 2021. Results In 2020, group A experienced a total of 8 RTIs, which affected 6 out of 8 patients (75%); group B reported 21 RTIs, with at least one event in 11 out of 16 patients (68.7%). In 2021, RTIs affected 2 out of 8 patients (25%) in group A (p<0.02), and 13 out of 16 patients (81.2%) in group B (within this group, 5 patients had two RTIs). The RTIs' cumulative incidence over the observation period significantly differed between groups (66.7% in group A vs. 24.3% in group B; p<0.002), as well as the decrease in RTIs frequency from 2020 to 2021. No patients in group A were affected by COVID-19 during the observation period, while among controls, two patients had SARS-CoV-2 infection, notwithstanding three doses of vaccine. Conclusion This study suggests that bacterial lysates may provide clinical benefits for preventing RTIs. Additional research involving larger cohorts is required to verify the effectiveness of OM-85 in preventing RTIs in older adults.