Epidemiology, Clinical Characteristics, and Outcomes of Influenza-Associated Hospitalizations in US Children Over 9 Seasons Following the 2009 H1N1 Pandemic

Abstract

Background Recent population-based data are limited regarding influenza-associated hospitalizations in U.S. children. Methods We identified children <18 years hospitalized with laboratory-confirmed influenza during 2010–2019 seasons through CDC’s Influenza Hospitalization Surveillance Network. Adjusted hospitalization and in-hospital mortality rates were calculated, and multivariable logistic regression was conducted to evaluate risk factors for pneumonia, intensive care unit (ICU) admission, mechanical ventilation, and death. Results Over 9 seasons, adjusted influenza-associated hospitalization incidence rates ranged from 10–375 per 100,000 persons each season and were highest among infants <6 months. Rates decreased with increasing age. The highest in-hospital mortality rates were observed in children <6 months (0.73 per 100,000 persons). Over time, antiviral treatment significantly increased from 56% to 85% (P < .001) and influenza vaccination rates increased from 33% to 44% (P = .003). Among the 13,235 hospitalized children, 2,676 (20%) of hospitalized children were admitted to the ICU, 2,262 (17%) had pneumonia, 690 (5%) required mechanical ventilation, and 72 (0.5%) died during hospitalization. As compared with those <6 months of age, hospitalized children ≥13 years had higher odds of pneumonia (adjusted odds ratios [aOR], 2.7; 95% confidence interval [CI], 2.1–3.4), ICU admission (aOR, 1.6; 95% CI, 1.3–1.9), mechanical ventilation (aOR, 1.6; 95% CI, 1.1–2.2), and death (aOR, 3.3; 95% CI, 1.2–9.3). Conclusions Hospitalization and death rates were greatest in younger children at the population level. Among hospitalized children, however, older children had a higher risk of severe outcomes. Continued efforts to prevent and attenuate influenza in children are needed.

Inference of age‐dependent case‐fatality ratios for seasonal influenza virus subtypes A(H3N2) and A(H1N1)pdm09 and B lineages using data from the Netherlands

“…We applied the age‐group specific proportions from this aggregate data source (among <55 years only) to the total number of estimated deaths in the <55 years age‐group for each season, to estimate the number of influenza‐attributable deaths per 5‐year age‐group per season. This aggregate data source indicates a decreasing proportion with decreasing age‐group until 5–9 years (see Figure S3); the proportion for 1–4 years is higher than for 5–9 years and higher still for <1 year; this pattern is consistent with clinical data on rates of in‐hospital mortality among children hospitalised with confirmed influenza virus infection 31 …”

“…For this, we adopted the method implemented in DALY computation software 30 ); the proportion for 1-4 years is higher than for 5-9 years and higher still for <1 year; this pattern is consistent with clinical data on rates of in-hospital mortality among children hospitalised with confirmed influenza virus infection. 31…”

Trends and Changes in Influenza-associated Hospitalizations in Children During 25 Years in Finland, 1993–2018

“…Oseltamivir has been available for children since the early 2000s and for infants since 2012, and its use in hospitalized children has been widely recommended. 6,24 A recent study from the United States reported that between 2010–2011 and 2018–2019, the use of antiviral treatment in hospitalized children increased from 56% to 85%, 4 and a similar increasing trend was observed also in a Canadian study during the same seasons. 22 At our hospital, the use of oseltamivir has been routine for all hospitalized children since the early 2010s.…”

“…1 Despite many important advances seen in the field of influenza, influenza-associated hospitalizations are still common in children, and the highest rates are invariably reported among infants <6 months of age. 2–4…”

“…1 Despite many important advances seen in the field of influenza, influenza-associated hospitalizations are still common in children, and the highest rates are invariably reported among infants <6 months of age. [2][3][4] During the past several years, the measures available for prevention, treatment and diagnosis of influenza have expanded substantially. Current influenza vaccines have largely switched from trivalent to quadrivalent vaccines that can provide increased coverage against circulating strains of influenza, and new technologies to improve vaccine efficacy have been adopted.…”