Association Between Oseltamivir Timing and Clinical Outcomes in Hospitalized Children with Influenza: A Retrospective Cohort Study

Background: Influenza is one of the most common viruses causing an acute course illness, mainly targeting the respiratory system. It is a communicable disease that spreads easily between individuals and is usually self-limiting in most cases. However, complications of influenza are numerous, including secondary bacterial infections, exacerbation of underlying respiratory conditions, and central nervous system–related complications. The risk of influenza-related hospitalization and complications is increased in children younger than 5 years and in those with underlying chronic diseases. Three classes of antiviral therapy are used in the treatment of influenza: neuraminidase inhibitors, adamantanes, and inhibitors of influenza cap-dependent endonuclease. Oseltamivir is considered the mainstay therapy for influenza treatment. Objective: This study investigates the efficacy of early oseltamivir treatment compared to late treatment in improving recovery by reducing hospital length of stay and preventing influenza-related complications such as pneumonia, otitis media, and asthma exacerbations. Methodology: This retrospective study analyzed data from 280 pediatric patients admitted to a tertiary care hospital between January 2020 and April 2023. Included patients were aged 1 month to 14 years, had laboratory-confirmed influenza A or B by polymerase chain reaction or point-of-care rapid testing, and received oseltamivir during hospitalization. Early oseltamivir treatment was defined as initiation within 48 hours of symptom onset, whereas initiation after 48 hours was considered late. Results: The study included 151 (53.9%) males and 129 (46.1%) females. Children who received early oseltamivir treatment had a significantly shorter hospital length of stay of approximately one day (∼ 16– 19 hours) compared to those who started treatment after 48 hours mean ± SD: 3.28 ± 1.46 vs 3.95 ± 2.26 days; P = 0.007. A weak positive correlation was observed between time to oseltamivir initiation and hospital length of stay ( r = 0.13, P = 0.02). Early treatment was associated with a significantly lower incidence of pneumonia, otitis media, and acute asthma exacerbation compared to late treatment ( P < 0.05 for all). Conclusion: Early initiation of oseltamivir within 48 hours is effective in reducing hospital length of stay and preventing common influenza-related complications. Keywords: influenza, oseltamivir, influenza-related complications, hospital length of stay