1395. Influenza B-Associated Pediatric Mortality in the US Between 2010 and 2019

Abstract Background To assess the contribution of influenza B to mortality in the US pediatric population, we analyzed the proportion of influenza-associated pediatric mortality attributed to influenza A and B over nine influenza seasons using national surveillance data. The effectiveness of influenza vaccines against influenza B in the pediatric population was also assessed. Methods The study period was the 2010/11 to 2018/19 influenza seasons. Proportions of circulating strains in the general population and influenza-associated pediatric mortality for each season were obtained from annual Centers for Disease Control and Prevention Morbidity and Mortality Weekly Reports on influenza. A Chi-squared test with Yates’ correction was used to assess the contribution of influenza B to pediatric mortality relative to its circulation among influenza viruses. Consolidated vaccine effectiveness (VE) against influenza B for inactivated influenza vaccine (IIV) in the 2010/11 to 2017/18 seasons and live attenuated influenza vaccine (LAIV) in the 2010/11 to 2015/16 seasons were obtained from a published meta-analysis and annual US Flu VE Network studies. There were no US data on LAIV VE for 2016/17 and 2017/18. Results During the 2010/11 to 2018/19 seasons, influenza B accounted for 4.0%–29.2% of all circulating influenza strains. A/H3N2 viruses were the predominant circulating strain in most seasons. In the same period, influenza B accounted for 7.0%–54.1% of pediatric influenza-associated mortality (Figure). The proportion of influenza B-related deaths was significantly higher (p< 0.01) than what would have been expected based on the proportion of circulating influenza B strains in the general population, overall and in the 2010/11, 2012/13, 2016/17, and 2017/18 seasons. Point estimates of VE against influenza B for children aged 2–17 years ranged from 33%–70% for IIV between 2010/11 and 2017/18, and from 53%–82% for LAIV between 2010/11 and 2015/16. Proportion of circulating influenza B strains compared with influenza B-associated pediatric mortality in the US between the 2010/11 and 2018/19 seasons Conclusion During the study period, influenza B accounted for a disproportionate percentage of pediatric mortality in the US relative to its overall circulation. These data counter the perception that influenza B is less severe than influenza A in children and highlight the importance of influenza vaccination to prevent influenza and its complications. Disclosures Allyn Bandell, PharmD, AstraZeneca (Employee, Shareholder) Pedro Piedra, MD, Roche (Consultant)Shionogi (Grant/Research Support) Christopher S. Ambrose, MD, MBA, AstraZeneca (Employee, Shareholder) Ravi Jhaveri, MD, AbbVie (Grant/Research Support)Alios (Research Grant or Support)Gilead (Grant/Research Support)Medimmune/AstraZeneca (Employee)Merck (Grant/Research Support)Saol Therapeutics (Consultant)Seqirus (Consultant)