BACKGROUNDAntiadhesive compounds are promising candidates for prevention or treatment of infections. We have investigated the efficacy of such an agent, 3'-sialyllacto-N-neotetraose (NE-1530), given intranasally for prophylaxis of acute otitis media and for effect on nasopharyngeal carriage of bacteria.METHODSWe did a randomised, double-blind placebo-controlled study at one study site. 507 healthy children were randomly assigned either NE-1530 (n=254) or placebo (253) as intranasal sprays twice daily during 3 months. The children were examined by the study physicians once a month and during illness. Treatment efficacy was estimated from Cox proportional hazards model. A sample of nasopharyngeal secretion was taken at every visit for culture of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Adverse events were recorded in study diaries.FINDINGSAt least one event of acute otitis media was diagnosed in 108 (43%) of 254 children in the NE-1530 group and in 86 (34%) of 253 children in the placebo group. The efficacy of treatment was negative, -27% (95% CI -68 to 5; p=0.10). The nasopharyngeal carriage of S pneumoniae, H. influenzae, and M. catarrhalis was not affected by treatment, and the adverse event profiles were almost identical for NE-1530 and placebo.INTERPRETATIONNE-1530 did not have a beneficial effect on the occurrence of acute otitis media or on the nasopharyngeal carriage of bacteria in children.