Pre-Exposure Intranasal Treatment with Neomycin Sulfate Reduces Transmission of Influenza B Virus

Background/Objectives: Influenza B virus contributes substantially to annual morbidity and mortality, accounting for 20% to 30% of all influenza-associated deaths globally. Vaccination prevents severe disease, yet widely used inactivated influenza vaccines fail to reduce virus transmission. Also, influenza B viruses are less susceptible to commonly used antivirals than influenza A viruses. Therefore, new approaches are needed to decrease disease burden and limit virus spread. Neomycin, an aminoglycoside antibiotic, has recently been shown to mitigate SARS-CoV-2 transmission in a hamster model. In this study, we investigated the impact of neomycin on the transmission of influenza B virus. Methods: We used an influenza contact transmission model in guinea pigs and an aerosol transmission model in ferrets. Animals in experimental groups received intranasal neomycin sulphate (5 mg/guinea pig, 20 mg/ferret) or placebo one day before contact with infected animals and for four days thereafter. In the guinea pig experiment, an additional control group of animals was treated intranasally with interferon alpha. The virus spread from infected to contact animals was assessed by RT-PCR and viral culture of nasal washes during two weeks. Clinical signs and body weight were monitored daily. Results: In the guinea pig model, 75% of contact animals became infected with influenza B virus regardless of treatment. Neither neomycin nor interferon alpha prevented infection, although both delayed the onset of viral shedding in contact animals. In the ferret model, 33% of contact animals in the placebo group became infected, whereas no viral shedding was detected in the neomycin-treated group. Conclusions: Prophylactic intranasal neomycin treatment has the potential to protect exposed subjects from aerosol transmission of influenza B virus during flu outbreaks.