Behavioral Risk Factor Surveillance System (BRFSS)

Using BRFSS Data to Assess Influenza Vaccine Prevalence and Location

Data summaries related to influenza (flu) vaccination among workers were prepared using data from the BRFSS survey to help with planning future vaccination efforts. These summaries and the methodology to create them are described below. Additional estimates of seasonal flu vaccination coverage are available.

NIOSH assessed flu vaccination among currently employed workers who responded to the 2018 BRFSS survey. NIOSH researchers created data summaries by industry and occupation, which describe analyses of flu vaccine prevalence among these workers and where they received their flu vaccine. Respondents from the 30 states that asked the two questions on industry and occupation were included.

Flu Vaccine Prevalence Data

Study Population

For these analyses, the most recent year for which BRFSS industry and occupation data were available, 2018, was used. Thirty states asked the industry and occupation questions (see Data Description by Year for 2018 details).

Industry and Occupation

Survey participants who were currently employed at the time of their interview or who had been employed within the previous 12 months were asked the following questions to ascertain occupation and industry, respectively:

  • “What kind of work do you do? For example, registered nurse, janitor, cashier, auto mechanic” and
  • “What kind of business or industry do you work in? For example, hospital, elementary school, clothing manufacturing, restaurant.”

The free-text responses were coded to the 2010 version of the US Census Bureau industry and occupation numeric codes.external icon

The sample:

  • Included respondents who resided in the 30 states and were currently employed for wages or self-employed at the time of their interview but were not in the U.S. armed forces.
  • Excluded U.S. armed forces respondents because they receive vaccinations through the military and because the BRFSS data are not representative of active duty military.

Influenza Vaccination and Type of Place of Vaccination

Influenza vaccination prevalence was calculated from responses to this core question (which was asked of all participants):

“During the past 12 months, have you had either a flu shot or a flu vaccine that was sprayed in your nose?”

Possible responses were:

  • yes
  • no
  • don’t know/not sure
  • refused

Respondents who replied “yes” were asked:

“At what kind of place did you get your last flu shot or vaccine?”

Possible responses were:

  • doctor’s office or health maintenance organization (HMO)
  • health department
  • another type of clinic or health center (a community health center)
  • senior, recreation, or community center
  • store (supermarket, drug store)
  • hospital (inpatient)
  • emergency room
  • workplace
  • some other kind of place
  • school
  • received vaccination in Canada/Mexico
  • don’t know/not sure
  • refused

NIOSH researchers did not include missing responses or responses coded “don’t know/not sure” or “refused” in the analyses.

Data Analysis

  • Analyses were limited to currently employed participants who had codable, non-missing industry and occupation. Learn more about the coding scheme details.
  • Weighted data were analyzed to account for the complex BRFSS sampling design and to produce estimates representative of the states’ populations.
  • Crude prevalences were calculated to focus on the magnitude of the estimates.
  • The data were analyzed with Proc SURVEYFREQ in SAS version 9.4 (SAS Institute, Inc.).
  • Using BRFSS criteria, reporting of estimates was limited to those with a relative standard error (RSE) ≤ 30% and an unweighted denominator ≥ 50.


BRFSS data are self-reported and not confirmed by records. This is true for vaccination information and industry and occupation. Interpretation of questions by respondents and of industry and occupation responses by interviewers or during coding may lead to misclassification or to missing data if the responses were not clear enough to be codable. 11.3% of the industry responses, and 15.9% of the occupation responses were not codable due to missing or vague responses. These analyses included data from only the 30 participating states, and thus, the findings are not representative of the U.S. population.

There may have been misclassification of vaccine administration location, so this should be kept in mind during any evaluation or use of these results. Specifically, participants in certain industries and occupations may have been vaccinated at work but selected their work location (e.g., hospital, health department, school) rather than selecting “workplace” as their response.

Page last reviewed: May 14, 2021