Background Nearly half of all hospitalised infants with respiratory syncytial virus (RSV) lower respiratory tract disease (LRTD) are treated with (parenteral) antibiotics. We hypothesized that the use of antibiotics would not lead to a reduced duration of hospitalisation.

Methods Seventy-one patients <24 months of age with a virologically confirmed clinical diagnosis of RSV LRTD were randomized to azithromycin 10 mg/kg/day (N = 32) or placebo (N = 39) in a multi-centre, randomized, double-blind, placebo-controlled equivalence trial during three RSV seasons (2002–2004 through 2005–2006). Primary endpoint was duration of hospitalization, secondary endpoints included duration of oxygen supplementation and nasogastric tube feeding, course of RSV symptom score, number of PICU referrals and number of patients who received additional antibiotic treatment. Data were analyzed according to the intention-to-treat principle using the Mann-Whitney U test or chi-square test considering p<0.05 statistically significant.

Results Included patients were comparable with respect to baseline demographics, clinical characteristics, laboratory and roentgenologic investigations. The mean duration of hospitalisation was not significantly different between patients treated with azithromycin or placebo (132.0±10.8 versus 139.6±7.7 h, p = 0.328). Azithromycin was not associated with a stronger resolution of clinical symptoms represented by the RSV symptom score. Four patients were treated with antibiotics after 72 h, three of them were assigned to placebo (p = 0.406).

Conclusions Infants and young children with RSV lower respiratory tract disease do not benefit from routine treatment with antibiotics (ISRCTN number 86554663).