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Early estimates of seasonal influenza vaccine effectiveness - United States, January 2015.
MMWR Morb Mortal Wkly Rep 2015; 64(1):10-5MM

Abstract

In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months. Each season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine in preventing medically attended acute respiratory illness (ARI) associated with laboratory-confirmed influenza. This season, early estimates of influenza vaccine effectiveness are possible because of widespread, early circulation of influenza viruses. By January 3, 2015, 46 states were experiencing widespread flu activity, with predominance of influenza A (H3N2) viruses. This report presents an initial estimate of seasonal influenza vaccine effectiveness at preventing laboratory-confirmed influenza virus infection associated with medically attended ARI based on data from 2,321 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (Flu VE) during November 10, 2014-January 2, 2015. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age, sex, race/ethnicity, self-rated health, and days from illness onset to enrollment) against laboratory-confirmed influenza associated with medically attended ARI was 23% (95% confidence interval [CI] = 8%-36%). Most influenza infections were due to A (H3N2) viruses. This interim VE estimate is relatively low compared with previous seasons when circulating viruses and vaccine viruses were well-matched and likely reflects the fact that more than two-thirds of circulating A (H3N2) viruses are antigenically and genetically different (drifted) from the A (H3N2) vaccine component of 2014-15 Northern Hemisphere seasonal influenza vaccines. These early, low VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with the currently circulating A (H3N2) viruses as well as other viruses that might circulate later in the season, including influenza B viruses. Even when VE is reduced, vaccination still prevents some illness and serious influenza-related complications, including thousands of hospitalizations and deaths. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated, including persons who might already have been ill with influenza this season.

Authors

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Pub Type(s)

Journal Article

Language

eng

PubMed ID

25590680

Citation

Flannery, Brendan, et al. "Early Estimates of Seasonal Influenza Vaccine Effectiveness - United States, January 2015." MMWR. Morbidity and Mortality Weekly Report, vol. 64, no. 1, 2015, pp. 10-5.
Flannery B, Clippard J, Zimmerman RK, et al. Early estimates of seasonal influenza vaccine effectiveness - United States, January 2015. MMWR Morb Mortal Wkly Rep. 2015;64(1):10-5.
Flannery, B., Clippard, J., Zimmerman, R. K., Nowalk, M. P., Jackson, M. L., Jackson, L. A., ... Fry, A. M. (2015). Early estimates of seasonal influenza vaccine effectiveness - United States, January 2015. MMWR. Morbidity and Mortality Weekly Report, 64(1), pp. 10-5.
Flannery B, et al. Early Estimates of Seasonal Influenza Vaccine Effectiveness - United States, January 2015. MMWR Morb Mortal Wkly Rep. 2015 Jan 16;64(1):10-5. PubMed PMID: 25590680.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Early estimates of seasonal influenza vaccine effectiveness - United States, January 2015. AU - Flannery,Brendan, AU - Clippard,Jessie, AU - Zimmerman,Richard K, AU - Nowalk,Mary Patricia, AU - Jackson,Michael L, AU - Jackson,Lisa A, AU - Monto,Arnold S, AU - Petrie,Joshua G, AU - McLean,Huong Q, AU - Belongia,Edward A, AU - Gaglani,Manjusha, AU - Berman,LaShondra, AU - Foust,Angie, AU - Sessions,Wendy, AU - Thaker,Swathi N, AU - Spencer,Sarah, AU - Fry,Alicia M, AU - ,, PY - 2015/1/16/entrez PY - 2015/1/16/pubmed PY - 2015/3/17/medline SP - 10 EP - 5 JF - MMWR. Morbidity and mortality weekly report JO - MMWR Morb. Mortal. Wkly. Rep. VL - 64 IS - 1 N2 - In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months. Each season since 2004-05, CDC has estimated the effectiveness of seasonal influenza vaccine in preventing medically attended acute respiratory illness (ARI) associated with laboratory-confirmed influenza. This season, early estimates of influenza vaccine effectiveness are possible because of widespread, early circulation of influenza viruses. By January 3, 2015, 46 states were experiencing widespread flu activity, with predominance of influenza A (H3N2) viruses. This report presents an initial estimate of seasonal influenza vaccine effectiveness at preventing laboratory-confirmed influenza virus infection associated with medically attended ARI based on data from 2,321 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (Flu VE) during November 10, 2014-January 2, 2015. During this period, overall vaccine effectiveness (VE) (adjusted for study site, age, sex, race/ethnicity, self-rated health, and days from illness onset to enrollment) against laboratory-confirmed influenza associated with medically attended ARI was 23% (95% confidence interval [CI] = 8%-36%). Most influenza infections were due to A (H3N2) viruses. This interim VE estimate is relatively low compared with previous seasons when circulating viruses and vaccine viruses were well-matched and likely reflects the fact that more than two-thirds of circulating A (H3N2) viruses are antigenically and genetically different (drifted) from the A (H3N2) vaccine component of 2014-15 Northern Hemisphere seasonal influenza vaccines. These early, low VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with the currently circulating A (H3N2) viruses as well as other viruses that might circulate later in the season, including influenza B viruses. Even when VE is reduced, vaccination still prevents some illness and serious influenza-related complications, including thousands of hospitalizations and deaths. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated, including persons who might already have been ill with influenza this season. SN - 1545-861X UR - https://www.unboundmedicine.com/medline/citation/25590680/Early_estimates_of_seasonal_influenza_vaccine_effectiveness___United_States_January_2015_ L2 - https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6401a4.htm DB - PRIME DP - Unbound Medicine ER -