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Disparities in the Severity of Influenza Illness: A Descriptive Study of Hospitalized and Nonhospitalized Novel H1N1 InfluenzaPositive Patients in New York City: 20092010 Influenza Season

Levy, Natalie S. MPH; Nguyen, Trang Quyen PhD, MPH; Westheimer, Emily MSc; Layton, Marcelle MD

Journal of Public Health Management & Practice: January/February 2013 - Volume 19 - Issue 1 - p 16–24
doi: 10.1097/PHH.0b013e31824155a2
Original Articles

Objective: To investigate the association between socioeconomic status (SES) and hospitalization for 2009 H1N1 influenza, independently of access to care and known risk factors for severe influenza illness, among New York City residents during the 2009–2010 influenza season.

Design: We used a 1:2 case-control study design, matching by age group and month of diagnosis. Cases were defined as laboratory-confirmed patients with 2009 H1N1 influenza who were hospitalized during their illness. Controls were defined as nonhospitalized laboratory-confirmed influenza A patients. Participants were contacted for a telephone interview to collect relevant clinical and demographic data. We used conditional logistic regression to analyze the association between SES and hospitalization.

Setting: New York City.

Participants: Of the 171 hospitalized cases who were identified between October 2009 and February 2010, a total of 128 completed telephone interviews. A total of 640 nonhospitalized controls were contacted, and of these, 337 completed interviews.

Main Outcome Measures: The main outcome of interest was whether or not a patient was hospitalized during his or her 2009 H1N1 influenza illness. Socioeconomic status was measured using education and neighborhood poverty.

Results: We identified a gradient in the odds of hospitalization for 2009 H1N1 influenza by education level among adults. This association could not be entirely explained by access to care and underlying risk factors. An inverse association between odds of hospitalization and neighborhood poverty was also identified among adults and children.

Conclusions: This study suggests that individuals of lower SES were more vulnerable to severe illness during the 2009 H1N1 pandemic. Additional research is needed to help guide interventions to protect this population during future influenza pandemics.

This article describes a retrospective qualitative study that used process mapping to define steps involved in implementing public vaccination clinics. It also discusses positive outliers that were identified for H1N1 public vaccination efforts as well as information obtained from in-depth interviews with local health department staff about the context and mechanisms that led to successful public vaccination clinics.

New York City Department of Health and Mental Hygiene, Bureau of Communicable Disease New York City.

Correspondence: Trang Quyen Nguyen, PhD, MPH, New York City Department of Health and Mental Hygiene, Bureau of Communicable Disease, 42-09 28th St, CN-22a, WS OG-154, Queens, NY 11101 (

The authors thank Erlinda Amoroso, Susan Anderson, Mike Antwi, Alice Baptiste-Norville, Fazlul Chowdhury, Carolyn Cokes, Paula Del Rosso, Marie Dorsinville, Muhammad Iftekharuddin, Lucretia Jones, Yin Ling Leung, Michelle Middleton, Ann Murray, Daniel Osuagwu, Jose Poy, Sara Sahl, Anna Smorodina, Rajmohan Sunkara, and the BCD student interns for their assistance in data collection. They also thank Annie Fine, Beth Nivin, and Alaina Stoute for their assistance in the study design, Brooke Bregman for assisting with ensuring the quality of the data used in this analysis, and Scott Harper and James Hadler for thoughtful and critical review and feedback of the analyses and manuscript. Finally, this project would not have been possible without the dedication of the staff at the Public Health Laboratory and the sentinel hospitals as well as the hardworking data entry staff at the Bureau of Communicable Disease.

Ms Levy received funding from the de Beaumont Foundation through the New York City Department of Health and Mental Hygiene Epi Scholars Program.

The authors declare no conflicts of interest.

© 2013 Lippincott Williams & Wilkins, Inc.