343. Waning Vaccine Protection Against Influenza A (H3N2) Illness in Children and Older Adults During a Single Season
Session: Poster Abstract Session: Influenza Vaccine in Children and Adults
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
  • Belongia IDSA13 poster FINAL.pdf (2.0 MB)
  • Background: Recent studies have raised concerns that protection may decline with increasing time since vaccination. We assessed the temporal relationship between influenza vaccination and influenza A illness during a season when A (H3N2) was the only circulating subtype.

    Methods: Patients in a community cohort were recruited during a clinical encounter for acute respiratory illness ≤ 7 days duration during the 2007-08 season. RT-PCR was performed on nasal/nasopharyngeal swabs for influenza detection. Dates of influenza vaccination were determined by a validated immunization registry. The analysis included only vaccinated patients; influenza B cases were excluded. The association between vaccination interval (days from vaccination to illness onset) and influenza A test result was examined in a logistic regression model with adjustment for confounders. Effect modification by age was assessed in an interaction term.

    Results: There were 629 vaccinated study participants, including 177 (28%) cases of influenza A (H3N2) and 452 test negative controls. The mean (SD) interval from vaccination to illness onset was 101.7 (25.9) days for influenza cases and 93.0 (29.9) days for controls. In the multivariable model, there was significant effect modification between the vaccination interval, age group, and influenza test result.  Among individuals <18 years old and those ≥ 65 years old, influenza A (H3N2) illness was associated with increasing time from vaccination to illness onset. For each 14 day increase in the vaccination interval, the adjusted probability of influenza A illness increased by an average of 5.0% and 2.5%, respectively, among adults ≥ 65 years old and children < 18 years old.  The results were similar when calendar week of vaccination was evaluated as the primary exposure variable.

    Conclusion: Identification of influenza A (H3N2) was associated with increasing time since vaccination among children and older adults with acute respiratory illness during a single influenza season. This observation is consistent with waning protection from inactivated vaccine, but minor antigenic drift may have contributed.

    Edward Belongia, MD1, Maria Sundaram, MSPH1, David Mcclure, PhD1, Jennifer Meece, PhD1, Jill Ferdinands, PhD, MSc2 and Jeffrey Vanwormer, PhD1, (1)Marshfield Clinic Research Foundation, Marshfield, WI, (2)Influenza Division, US Centers for Disease Control and Prevention, Atlanta, GA


    E. Belongia, MedImmune LLC: Grant Investigator, Research grant

    M. Sundaram, None

    D. Mcclure, None

    J. Meece, MedImmune, LLC: Grant Investigator, Research support

    J. Ferdinands, None

    J. Vanwormer, None

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