M A J O R A R T I C L E
Influenza Vaccine Effectiveness in the United States During 2012–2013: Variable Protection by Age and Virus Type
Huong Q. McLean,1 Mark G. Thompson,2 Maria E. Sundaram,1 Burney A. Kieke,1 Manjusha Gaglani,3 Kempapura Murthy,3
Pedro A. Piedra,4 Richard K. Zimmerman,5 Mary Patricia Nowalk,5 Jonathan M. Raviotta,5 Michael L. Jackson,6
Lisa Jackson,6 Suzanne E. Ohmit,7 Joshua G. Petrie,7 Arnold S. Monto,7 Jennifer K. Meece,1 Swathi N. Thaker,2
Jessie R. Clippard,2 Sarah M. Spencer,2 Alicia M. Fry,2 and Edward A. Belongia1
1Marshfield Clinic Research Foundation, Wisconsin; 2Centers for Disease Control and Prevention, Atlanta, Georgia; 3Baylor Scott and White Health, Texas A&M Health Science Center College of Medicine, Temple, and 4Baylor College of Medicine, Houston, Texas; 5University of Pittsburgh, Pennsylvania; 6Group Health Cooperative, Seattle, Washington; and 7University of Michigan, Ann Arbor
Background. During the 2012–2013 influenza season, there was cocirculation of influenza A(H3N2) and 2 in- fluenza B lineage viruses in the United States.
Methods. Patients with acute cough illness for ≤7 days were prospectively enrolled and had swab samples ob- tained at outpatient clinics in 5 states. Influenza vaccination dates were confirmed by medical records. The vaccine effectiveness (VE) was estimated as [100% × (1− adjusted odds ratio)] for vaccination in cases versus test-negative controls.