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Clin Infect Dis. (2012) doi: 10.1093/cid/cis574 First published online: July 25, 2012
Effectiveness of Seasonal Influenza Vaccines in the United States During a Season With Circulation of All Three Vaccine Strains
John J. Treanor1,
H. Keipp Talbot2,
Suzanne E. Ohmit5,
Laura A. Coleman6,
Mark G. Thompson7,
Po-Yung Cheng7,
Joshua G. Petrie5,
Geraldine Lofthus1,
Jennifer K. Meece6,
John V. Williams2,3,
LaShondra Berman7,
Caroline Breese Hall1,
Arnold S. Monto5,
Marie R. Griffin2,4,
Edward Belongia6,
David K. Shay7, and
for the US Flu-VE Network
+ Author Affiliations
1Department of Medicine, University of Rochester Medical Center, New York
2Department of Medicine and Pediatrics
3Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine
4Mid-South Geriatric Research Education and Clinical Center, VA Tennessee Valley Health Care System, Nashville, Tennessee
5Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor
6Marshfield Clinic Research Foundation, Marshfield, Wisconsin
7Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia
Correspondence: John Treanor, MD, University of Rochester, Medical Center, Rm 3-6209, 601 Elmwood Ave, Rochester, NY 14642 (john_treanor@urmc.rochester.edu).
Abstract
Background. Influenza vaccines may be reformulated annually because of antigenic drift in influenza viruses. However, the relationship between antigenic characteristics of circulating viruses and vaccine effectiveness (VE) is not well understood. We conducted an assessment of the effectiveness of US influenza vaccines during the 2010?2011 season.
Methods. We performed a case?control study comparing vaccination histories between subjects with acute respiratory illness with positive real-time reverse transcription polymerase chain reaction for influenza and influenza test-negative controls. Subjects with acute respiratory illness of ≤7 days duration were enrolled in hospitals, emergency departments, or outpatient clinics in communities in 4 states. History of immunization with the 2010?2011 vaccine was ascertained from vaccine registries or medical records. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, age, race, insurance status, enrollment site, and presence of a high-risk medical condition.
Results. A total of 1040 influenza-positive cases and 3717 influenza-negative controls were included from the influenza season, including 373 cases of influenza A(H1N1), 334 cases of influenza A(H3N2), and 333 cases of influenza B. Overall adjusted VE was 60% (95% confidence interval [CI], 53%?66%). Age-specific VE estimates ranged from 69% (95% CI, 56%?77%) in children aged 6 months?8 years to 38% (95% CI, −16% to 67%) in adults aged ≥65 years.
Conclusions. The US 2010?2011 influenza vaccines were moderately effective in preventing medically attended influenza during a season when all 3 vaccine strains were antigenically similar to circulating viruses. Continued monitoring of influenza vaccines in all age groups is important, particularly as new vaccines are introduced.
Effectiveness of Seasonal Influenza Vaccines in the United States During a Season With Circulation of All Three Vaccine Strains
John J. Treanor1,
H. Keipp Talbot2,
Suzanne E. Ohmit5,
Laura A. Coleman6,
Mark G. Thompson7,
Po-Yung Cheng7,
Joshua G. Petrie5,
Geraldine Lofthus1,
Jennifer K. Meece6,
John V. Williams2,3,
LaShondra Berman7,
Caroline Breese Hall1,
Arnold S. Monto5,
Marie R. Griffin2,4,
Edward Belongia6,
David K. Shay7, and
for the US Flu-VE Network
+ Author Affiliations
1Department of Medicine, University of Rochester Medical Center, New York
2Department of Medicine and Pediatrics
3Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine
4Mid-South Geriatric Research Education and Clinical Center, VA Tennessee Valley Health Care System, Nashville, Tennessee
5Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor
6Marshfield Clinic Research Foundation, Marshfield, Wisconsin
7Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia
Correspondence: John Treanor, MD, University of Rochester, Medical Center, Rm 3-6209, 601 Elmwood Ave, Rochester, NY 14642 (john_treanor@urmc.rochester.edu).
Abstract
Background. Influenza vaccines may be reformulated annually because of antigenic drift in influenza viruses. However, the relationship between antigenic characteristics of circulating viruses and vaccine effectiveness (VE) is not well understood. We conducted an assessment of the effectiveness of US influenza vaccines during the 2010?2011 season.
Methods. We performed a case?control study comparing vaccination histories between subjects with acute respiratory illness with positive real-time reverse transcription polymerase chain reaction for influenza and influenza test-negative controls. Subjects with acute respiratory illness of ≤7 days duration were enrolled in hospitals, emergency departments, or outpatient clinics in communities in 4 states. History of immunization with the 2010?2011 vaccine was ascertained from vaccine registries or medical records. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, age, race, insurance status, enrollment site, and presence of a high-risk medical condition.
Results. A total of 1040 influenza-positive cases and 3717 influenza-negative controls were included from the influenza season, including 373 cases of influenza A(H1N1), 334 cases of influenza A(H3N2), and 333 cases of influenza B. Overall adjusted VE was 60% (95% confidence interval [CI], 53%?66%). Age-specific VE estimates ranged from 69% (95% CI, 56%?77%) in children aged 6 months?8 years to 38% (95% CI, −16% to 67%) in adults aged ≥65 years.
Conclusions. The US 2010?2011 influenza vaccines were moderately effective in preventing medically attended influenza during a season when all 3 vaccine strains were antigenically similar to circulating viruses. Continued monitoring of influenza vaccines in all age groups is important, particularly as new vaccines are introduced.
