Decreased risk of non-influenza respiratory infection after influenza B virus infection in children.

Previous studies suggest that influenza virus infection may provide temporary non-specific immunity and hence lower the risk of non-influenza respiratory virus infection. In a randomized controlled trial of influenza vaccination, 1 330 children were followed-up in 2009-2011. Respiratory swabs were collected when they reported acute respiratory illness and tested against influenza and other respiratory viruses. We used Poisson regression to compare the incidence of non-influenza respiratory virus infection before and after influenza virus infection. Based on 52 children with influenza B virus infection, the incidence rate ratio (IRR) of non-influenza respiratory virus infection after influenza virus infection was 0.47 (95% confidence interval: 0.27-0.82) compared with before infection. Simulation suggested that this IRR was 0.87 if the temporary protection did not exist. We identified a decreased risk of non-influenza respiratory virus infection after influenza B virus infection in children. Further investigation is needed to determine if this decreased risk could be attributed to temporary non-specific immunity acquired from influenza virus infection.

Influenza versus other respiratory viruses - assessing severity among hospitalised children, Belgium, 2011 to 2020.

BackgroundKnowledge on the burden attributed to influenza viruses vs other respiratory viruses in children hospitalised with severe acute respiratory infections (SARI) in Belgium is limited.AimThis observational study aimed at describing the epidemiology and assessing risk factors for severe disease.MethodsWe retrospectively analysed data from routine national sentinel SARI surveillance in Belgium. Respiratory specimens collected during winter seasons 2011 to 2020 were tested by multiplex real-time quantitative PCR (RT-qPCR) for influenza and other respiratory viruses. Demographic data and risk factors were collected through questionnaires. Patients were followed-up for complications or death during hospital stay. Analysis focused on children younger than 15 years. Binomial logistic regression was used to identify risk factors for severe disease in relation to infection status.ResultsDuring the winter seasons 2011 to 2020, 2,944 specimens met the study case definition. Complications were more common in children with underlying risk factors, especially asthma (adjusted risk ratio (aRR): 1.87; 95% confidence interval (CI): 1.46-2.30) and chronic respiratory disease (aRR: 1.88; 95% CI: 1.44-2.32), regardless of infection status and age. Children infected with non-influenza respiratory viruses had a 32% higher risk of complications (aRR: 1.32; 95% CI: 1.06-1.66) compared with children with influenza only.ConclusionMulti-virus testing in children with SARI allows a more accurate assessment of the risk of complications and attribution of burden to respiratory viruses beyond influenza. Children with asthma and respiratory disease should be prioritised for clinical care, regardless of their virological test result and age, and targeted for prevention campaigns.