Background(Buccalin ®) is a Bacterial Lysates (BL) that belongs to a family of immune-stimulators, developed more than 30 years ago and it still has a role in the prophylaxis of Recurrent Respiratory Tract Infections (RRTI). However, original studies were conducted with an approach that does not seem to be aligned with the present methodologies. In addition, concomitant therapies substantially improved in the last decades. These two reasons strongly suggested to update our knowledge on the capacity of this bacterial lysate (Buccalin ®) to reduce the number of days with infectious episodes in patients with RRTI.MethodsA double blind, placebo-controlled, randomized, multicentre study was programmed (EudraCT code: 2011-005187-25). The reduction of the number of days with infectious episodes (IE) was the primary endpoint. Secondary endpoints were the number of IE, the use of concomitant drugs, the efficacy on signs and symptoms of RRTI and the safety of the drug. Patients were treated according to the registered schedule and were followed up for a period of 6 months.ResultsFrom a cohort of 188 patients eligible for the study, 90 were included in the active group and 88 in the placebo group. The study was completed in 170 patients. A significant reduction of the number of days with IE was observed (6.57 days in the active group and 7.47 in the placebo group). Secondary endpoints were only partially achieved. No virtual adverse events related to the treatment were recorded.ConclusionThe administration of bacterial lysate (Buccalin ®) in patients with RRTI had the capacity to significantly reduce the number of days with IE in a multicentre, randomized, placebo controlled, clinical study. The treatment was safe. Of note, all patients were free to be treated with the best concomitant therapies. In these conditions, the positive results observed demonstrated that this bacterial lysate has maintained its capacity of reducing the days with infections in patients with RRTI, also in association to the concomitant therapies available nowadays.