1353. Does Influenza Vaccination Modify Influenza Disease Severity? Data on Adults Hospitalized with Influenza during the 2013−14 Season in the United States
Session: Oral Abstract Session: Vaccines for Seasonal and Avian Flu: Who Knew?
Saturday, October 10, 2015: 9:15 AM
Room: 5--AB
Background: Influenza vaccination might modify the severity of influenza outcomes in vaccinated persons who become infected. We investigated the effect of influenza vaccination on influenza disease severity in adults hospitalized with laboratory-confirmed influenza during a season in which influenza vaccine strains were antigenically similar to strains causing disease in the community.

Methods: We analyzed influenza vaccination and influenza severity using Influenza Hospitalization Surveillance Network (FluSurv-NET) data for the 2013−14 influenza season (n=5,628). Death, intensive care unit (ICU) admission, and hospital and ICU lengths of stay (LOS) served as measures of disease severity. We categorized age into three groups: 18–49, 50–64, and ≥65 years. For each age group, data were analyzed by multivariable logistic regression (MLR) and proportional hazard models (PHM), adjusting for age, sex, race, body mass index, underlying medical conditions, and timing of antiviral treatment. In addition, we performed propensity score matching (PSM) to control for the probability of vaccination. We present adjusted odds ratios (aOR) for death and ICU admission and hazard ratios (aHR) for ICU or hospital discharge using PSM.

Results: For those aged 18–49 years, we found a protective effect of the vaccine for ICU admission (aOR=0.67; 95% CI: 0.47−0.97) and ICU LOS (aHR=1.53; 95% CI: 1.06−2.20) with and without PSM and for hospital LOS (aHR=1.18; 95% CI: 1.01−1.38) with PSM only. For those aged 50–64 years, we found a protective effect of the vaccine for in-hospital death (aOR=0.48; 95% CI: 0.27−0.86), ICU LOS (aHR=1.49; 95% CI: 1.15−1.93), and hospital LOS (aHR for discharge =1.26; 95% CI: 1.13−1.41) with and without PSM. Similarly, for those aged ≥65 years, we found a protective effect of the vaccine for in-hospital death (aOR=0.39; 95% CI: 0.18−0.82), ICU admission (aOR=0.58; 95% CI: 0.41−0.81), and hospital LOS (aHR=1.16; 95% CI: 1.03−1.32) with and without PSM.

Conclusion: Our findings show a protective effect of influenza vaccination on influenza disease severity among hospitalized adults during the 2013−14 season. We may observe similar effects in other seasons where influenza vaccine viruses match circulating viruses.

Carmen Arriola, DVM, PhD, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA; Epidemic Intelligence Service Program, Centers for Disease Control and Prevention, Atlanta, GA, Evan J. Anderson, MD, Atlanta Veterans Affairs Medical Center, Atlanta, GA; Pediatrics and Medicine, Emory University School of Medicine, Atlanta, GA, Marisa Bargsten, MPH, New Mexico Department of Health, Santa Fe, NM, Susan Bohm, MS, Michigan Department of Health and Human Services, Lansing, MI, Mary Lou Lindegren, MD, MPH, Vanderbilt University School of Medicine, Nashville, TN, Krista Lung, BS, Bureau of Infectious Diseases, Ohio Department of Health, Columbus, OH, Ruth Lynfield, MD, FIDSA, Minnesota Department of Health, St. Paul, MN, Lisa Miller, MD, MSPH, Colorado Department of Public Health and Environment, Denver, CO, Maya Monroe, MPH, Maryland Department of Health and Mental Hygiene, Baltimore, MD, Arthur Reingold, MD, FIDSA, University of California - Berkeley, Berkeley, CA, Ann Thomas, MD, MPH, Department of Human Services, Health Services, Portland, OR, Kimberly Yousey-Hindes, MPH, CPH, Emerging Infections Program, Yale, New Haven, CT and Sandra Dos Santos Chaves, MD, Centers for Disease Control and Prevention, Atlanta, GA

Disclosures:

C. Arriola, None

E. J. Anderson, Abbvie: Consultant , Consulting fee
MedImmune: Investigator , Research grant
Roche: Editorial assistance in writing a manuscript , Editorial assistance in writing a manuscript

M. Bargsten, None

S. Bohm, None

M. L. Lindegren, None

K. Lung, None

R. Lynfield, None

L. Miller, None

M. Monroe, None

A. Reingold, None

A. Thomas, None

K. Yousey-Hindes, None

S. Dos Santos Chaves, None

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