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Vaccine. 2018 Feb 28;36(10):1272-1278. doi: 10.1016/j.vaccine.2018.01.045.

Influenza vaccine effectiveness in older adults compared with younger adults over five seasons.

Author information

1
Epidemic Intelligence Service, CDC, United States; Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, United States. Electronic address: vnt0@cdc.gov.
2
Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, United States.
3
University of Michigan and Henry Ford Health System, United States.
4
Marshfield Clinic Research Institute, United States.
5
Baylor Scott and White Health, Texas A&M University Health Science Center College of Medicine, United States.
6
University of Pittsburgh Schools of the Health Sciences and UPMC, United States.
7
Kaiser Permanente Washington Health Research Institute, United States.

Abstract

BACKGROUND:

There have been inconsistent reports of decreased vaccine effectiveness (VE) against influenza viruses among older adults (aged ≥ 65 years) compared with younger adults in the United States. A direct comparison of VE over multiple seasons is needed to assess the consistency of these observations.

METHODS:

We performed a pooled analysis of VE over 5 seasons among adults aged ≥ 18 years who were systematically enrolled in the U.S. Flu VE Network. Outpatients with medically-attended acute respiratory illness (cough with illness onset ≤ 7 days prior to enrollment) were tested for influenza by reverse transcription polymerase chain reaction. We compared differences in VE and vaccine failures among older adult age group (65-74, ≥75, and ≥ 65 years) to adults aged 18-49 years by influenza type and subtype using interaction terms to test for statistical significance and stratified by prior season vaccination status.

RESULTS:

Analysis included 20,022 adults aged ≥ 18 years enrolled during the 2011-12 through 2015-16 influenza seasons; 4,785 (24%) tested positive for influenza. VE among patients aged ≥ 65 years was not significantly lower than VE among patients aged 18-49 years against any subtype with no significant interaction of age and vaccination. VE against A(H3N2) viruses was 14% (95% confidence interval [CI] -14% to 36%) for adults ≥ 65 years and 21% (CI 9-32%) for adults 18-49 years. VE against A(H1N1)pdm09 was 49% (95% CI 22-66%) for adults ≥ 65 years and 48% (95% CI 41-54%) for adults 18-49 years and against B viruses was 62% (95% CI 44-74%) for adults ≥ 65 years and 55% (95% CI 45-63%) for adults 18-49 years. There was no significant interaction of age and vaccination for separate strata of prior vaccination status.

CONCLUSIONS:

Over 5 seasons, influenza vaccination provided similar levels of protection among older and younger adults, with lower levels of protection against influenza A(H3N2) in all ages.

KEYWORDS:

Human; Influenza; Influenza vaccine effectiveness; Influenza vaccines; Older adults

PMID:
29402578
PMCID:
PMC5812289
DOI:
10.1016/j.vaccine.2018.01.045
[Indexed for MEDLINE]
Free PMC Article

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