Neighborhood Disparities in Influenza and Influenza like Illness Hospitalization During Seasonal and Pandemic Influenza.

Background: Between 2010 and 2024, 120 000-710 000 people were hospitalized for influenza in the United States each year. In the current century there has been one influenza pandemic so far, causing widespread infection, hospitalization, and deaths. While prior research has examined neighborhood and individual racial and socioeconomic disparities in influenza outcomes during seasonal or pandemic influenza, there is limited understanding of whether the associations between neighborhood social determinants and influenza outcomes differ between seasonal and pandemic influenza. Methods: Using Health Care Utilization Project hospitalization data from New York State from 2009-2013, covering the 2009 H1N1 pandemic and seasonal influenza in the following years, we computed the relative index of inequality (RII) in influenza hospitalization rates associated with neighborhood social and economic factors. Results: All neighborhood factors showed significant associations with hospitalization, although the magnitude of the disparities differed by neighborhood factor, and disparities were generally slightly wider in pandemic influenza periods, although differences between periods were small. The widest hospitalization rate disparity for pandemic and seasonal influenza periods was for median household income (pandemic RII, 2.39 [95% confidence interval, 2.16-2.63]; seasonal RII, 2.34 [2.10-2.60]); the factor with the largest difference between pandemic and seasonal periods was poverty (pandemic and seasonal RIIs, 2.11 and 1.84, respectively). Conclusions: Our findings demonstrate the persistence of neighborhood inequities in influenza hospitalizations in both pandemic and seasonal periods and suggest the importance of investing in structural conditions to address health inequities.