1. Trends of influenza vaccination coverage among adult populations, United States, 2010-2016
Peng-jun Lu, MD, PhD1; Mei-Chun Hung, MPH, PhD1,2 ; Alissa C. O’Halloran, MSPH3; Helen Ding, MD, MSPH1, 4; Walter W. Williams, MD, MPH1; James A. Singleton, PhD1
1 Immunization Services Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, NE, Atlanta, GA 30333
2 Leidos, Inc, Atlanta, GA
3 Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, NE, Atlanta, GA 30333
4 CFD Research Corporation, Huntsville, AL, 35806
Disclaimer: The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of CDC.

2. BACKGROUND Vaccination can reduce influenza disease burden
The estimated numbers of flu illnesses, medical visits, and hospitalizations
prevented by flu vaccination during the season were 5.0
million, 2.5 million, and 71,000, respectively
Prior to 2010, the adult groups recommended for annual vaccination included persons aged >50 years, pregnant women, persons aged years with high-risk conditions, healthcare personnel, and close contacts of high-risk persons
Since the influenza season, the Advisory Committee on Immunization Practices (ACIP) has recommended annual influenza vaccination for all persons ≥6 months of age

3. OBJECTIVE The objectives of this study were:
To assess influenza vaccination in each of the through seasons, for persons aged ≥18, 18-49, 50-64, and ≥65 years, health care personnel (HCP), and pregnant women ( through seasons)
To identify factors independently associated with vaccination

4. METHODS
Data from the National Health Interview Survey (NHIS) were analyzed to determine influenza vaccination coverage among adult populations
To better assess influenza vaccination coverage for each season, we reported coverage restricted to individuals interviewed during August through June, and vaccinated during July through May, using the Kaplan-Meier survival analysis procedure. For example, respondents interviewed during August 2015 through June 2016 were analyzed to estimate influenza vaccination received during July 2015 through May 2016 for influenza season
Vaccination month and year were imputed for individuals who reported they received vaccination but did not report their month and year of vaccination
Vaccination status was determined using reported month and year of most recent vaccination as of the end of the month prior to interview
T test for linear trends in recent years was conducted for each group
Multivariable logistic regression analysis was conducted to assess factors associated with vaccination among respondents interviewed during August 2015 through June 2016, and vaccination status was determined by whether individuals received vaccination in the previous 12 months or not
Estimates were weighted to the adult civilian population of the United States

5. Influenza vaccination coverage among adults ≥18 years by age groups, and among healthcare personnel and pregnant women, United States, season
age (≥ 1 dose) among travelers ≥18 years by age groups, United States, 2015
among travelers ≥18 years by age groups, United States, 2015
ge groups, United States, 2015
Source: National Health Interview Survey

6. Influenza vaccination coverage among adults ≥18 years by age groups and high-risk conditions, United States, season
age (≥ 1 dose) among travelers ≥18 years by age groups, United States, 2015
among travelers ≥18 years by age groups, United States, 2015
ge groups, United States, 2015
Source: National Health Interview Survey

7. Influenza vaccination coverage among selected US adult populations, through the season.
Overall, influenza vaccination coverage among adults ≥18 years and years without high-risk conditions increased significantly from 38.3% and 24.5%, respectively in the season to 43.4% and 31.6%, respectively in the season, with annual average increases of 1.3% and 1.7%, respectively (p<0.05). Coverage among persons aged years with high-risk conditions were significantly higher compared with those without high-risk conditions over years.
Source: National Health Interview Survey

8. Trends of influenza vaccination coverage among selected US adult ≥18 years by race/ethnicity, through the season
Overall, for persons aged ≥18 years, influenza vaccination among non-Hispanic whites, non-Hispanic blacks, Hispanics, and others significantly increased from the to seasons. Coverage was lower among non-Hispanic blacks and Hispanics compared with non-Hispanic whites from the to seasons.
Source: National Health Interview Survey,

9. RESULTS - BIVARIABLE
Vaccination coverage among adults ≥18 years significantly increased from 38.3% in to 43.4% in , with an average increase of 1.3 percentage point annually
From the through seasons, coverage was stable for adults ≥65 years, and changed by percentage points for all other subgroups examined
Overall, for persons aged ≥18 years, influenza vaccination among non-Hispanic whites, non-Hispanic blacks, Hispanics, and others significantly increased from the to seasons. Coverage was lower among non-Hispanic blacks and Hispanics compared with non-Hispanic whites from the to seasons
Among HCP, influenza vaccination increased from 55.9% in the season to 64.8% in the season, with an annual average increase of 1.9 percentage points
Among pregnant women, influenza vaccination increased from 40.4% in the season to 50.3% in the season, with an annual average increase of 2.6 percentage points
Coverage in was 70.4% for adults >65 years, 46.4% for years, 32.3% for years, 64.8% for HCP, and 50.3% for pregnant women. Coverage was significantly higher among persons with high-risk conditions compared with those without high-risk conditions

10. RESULTS - MULTIVARIABLE
Characteristics independently associated with increased vaccination among adults aged ≥18 years during the influenza season were:
Being Asian
Being married
Having higher education
Not being employed
Having one or more physician contacts
Hospitalized in past 12 months
Having a usual place for health care
Having health insurance
Being HCP
Additionally, younger age, and being non-Hispanic blacks were independently associated with a decreased likelihood of vaccination

11. Limitations
Information on influenza vaccination was self-reported and may be subject to recall bias. However, self-reported seasonal influenza vaccination status among adults has been shown to have relatively high agreement with vaccination status ascertained from medical records
High-risk conditions were self-reported and not validated by medical record review
Because our sample was limited to non-institutionalized civilian adults, generalization may not be made beyond this population

12. Opportunities for Improvement
Influenza vaccination coverage among persons aged ≥18 years, HCP, and pregnant women remained suboptimal. Vaccination coverage varied widely by race/ethnicity, age, and risk groups
Substantial improvement in annual influenza vaccination is needed to maximally reduce the health impact of influenza
Expanded access through greater use of complimentary settings and vaccine providers, and better use of evidence-based practices at medical sites (e.g., standing orders, and reminder/recall notification) are important to improve influenza vaccination coverage