Influenza-Related Hospitalizations and Poverty Levels - United States, 2010-2012.

Annual influenza vaccine is recommended for all persons aged ≥6 months in the United States, with recognition that some persons are at risk for more severe disease (1). However, there might be previously unrecognized demographic groups that also experience higher rates of serious influenza-related disease that could benefit from enhanced vaccination efforts. Socioeconomic status (SES) measures that are area-based can be used to define demographic groups when individual SES data are not available (2). Previous surveillance data analyses in limited geographic areas indicated that influenza-related hospitalization incidence was higher for persons residing in census tracts that included a higher percentage of persons living below the federal poverty level (3-5). To determine whether this association occurs elsewhere, influenza hospitalization data collected in 14 FluSurv-NET sites covering 27 million persons during the 2010-11 and 2011-12 influenza seasons were analyzed. The age-adjusted incidence of influenza-related hospitalizations per 100,000 person-years in high poverty (≥20% of persons living below the federal poverty level) census tracts was 21.5 (95% confidence interval [CI]: 20.7-22.4), nearly twice the incidence in low poverty (<5% of persons living below the federal poverty level) census tracts (10.9, 95% CI: 10.3-11.4). This relationship was observed in each surveillance site, among children and adults, and across racial/ethnic groups. These findings suggest that persons living in poorer census tracts should be targeted for enhanced influenza vaccination outreach and clinicians serving these persons should be made aware of current recommendations for use of antiviral agents to treat influenza (6).

Does Influenza Vaccination Modify Influenza Severity? Data on Older Adults Hospitalized With Influenza During the 2012-2013 Season in the United States.

BACKGROUND: Some studies suggest that influenza vaccination might be protective against severe influenza outcomes in vaccinated persons who become infected. We used data from a large surveillance network to further investigate the effect of influenza vaccination on influenza severity in adults aged ≥50 years who were hospitalized with laboratory-confirmed influenza. METHODS: We analyzed influenza vaccination and influenza severity using Influenza Hospitalization Surveillance Network (FluSurv-NET) data for the 2012-2013 influenza season. Intensive care unit (ICU) admission, death, diagnosis of pneumonia, and hospital and ICU lengths of stay served as measures of disease severity. Data were analyzed by multivariable logistic regression, parametric survival models, and propensity score matching (PSM). RESULTS: Overall, no differences in severity were observed in the multivariable logistic regression model. Using PSM, adults aged 50-64 years (but not other age groups) who were vaccinated against influenza had a shorter length of ICU stay than those who were unvaccinated (hazard ratio for discharge, 1.84; 95% confidence interval, 1.12-3.01). CONCLUSIONS: Our findings show a modest effect of influenza vaccination on disease severity. Analysis of data from seasons with different predominant strains and higher estimates of vaccine effectiveness are needed.

Obesity not associated with severity among hospitalized adults with seasonal influenza virus infection.

We examined seasonal influenza severity [artificial ventilation, intensive care unit (ICU) admission, and radiographic-confirmed pneumonia] by weight category among adults hospitalized with laboratory-confirmed influenza. Using multivariate logistic regression models, we found no association between obesity or severe obesity and artificial ventilation or ICU admission; however, overweight and obese patients had decreased risk of pneumonia. Underweight was associated with pneumonia (adjusted odds ratio 1.31; 95 % confidence interval 1.04, 1.64).

Influenza Antiviral Treatment and Length of Stay.

BACKGROUND: Antiviral treatment is recommended for hospitalized patients with suspected and confirmed influenza, but evidence is limited among children. We evaluated the effect of antiviral treatment on hospital length of stay (LOS) among children hospitalized with influenza. METHODS: We included children <18 years hospitalized with laboratory-confirmed influenza in the US Influenza Hospitalization Surveillance Network. We collected data for 2 cohorts: 1 with underlying medical conditions not admitted to the ICU (n = 309, 2012-2013) and an ICU cohort (including children with and without underlying conditions; n = 299, 2010-2011 to 2012-2013). We used a Cox model with antiviral receipt as a time-dependent variable to estimate hazard of discharge and a Kaplan-Meier survival analysis to determine LOS. RESULTS: Compared with those not receiving antiviral agents, LOS was shorter for those treated ≤2 days after illness onset in both the medical conditions (adjusted hazard ratio: 1.37, P = .02) and ICU (adjusted hazard ratio: 1.46, P = .007) cohorts, corresponding to 37% and 46% increases in daily discharge probability, respectively. Treatment ≥3 days after illness onset had no significant effect in either cohort. In the medical conditions cohort, median LOS was 3 days for those not treated versus 2 days for those treated ≤2 days after symptom onset (P = .005). CONCLUSIONS: Early antiviral treatment was associated with significantly shorter hospitalizations in children with laboratory-confirmed influenza and high-risk medical conditions or children treated in the ICU. These results support Centers for Disease Control and Prevention recommendations for prompt empiric antiviral treatment in hospitalized patients with suspected or confirmed influenza.