Codes and Frequencies
For sample adults and sample children who had a flu vaccine in the past 12 months, VACFLUYR reports the calendar year of the person's most recent flu vaccine. For the associated month of the most recent flu vaccine, see VACFLUMO. Beginning in 2019, the universe is further restricted to those who gave the month or don’t know the month of the vaccine dose.
See the Comparability Tab for additional information about changes to the universe and construction of this variable over time as well as information about seasonal flu versus H1N1 flu vaccinations in 2009-2011.
In 2005-2015 for sample adults, and 2005-August 10, 2010 for sample children, the survey asked whether sample persons had a flu shot vaccine (VACFLUSH12M), and also asked if they had a flu nasal spray vaccine (VACFLUSP12M) in the past 12 months. For either mode of vaccination the sample person reported receiving in the past 12 months, they were asked for the month (VACFLUSHMO/VACFLUSPMO) and year (VACFLUSHYR/VACFLUSPYR) of their most recent vaccine by this mode.
More recent versions of the flu vaccine variables were structured differently
For sample children surveyed after August 10, 2010 in the 2010 NHIS sample and sample adults beginning in the 2016 NHIS sample, a streamlined set of questions about flu vaccines was asked. Sample persons were asked if they had received a flu vaccine in the past 12 months (VACFLU12M), then asked for the month (VACFLUMO) and year (VACFLUYR) of their most recent vaccine, as well as the mode of their most recent flu vaccine (choosing between a shot or nasal spray) (VACFLUMODE). Sample children were asked if they had more than one vaccination in the past year (VACFLUNUM) and could also report the mode (VAC2FLUMODE), month (VAC2FLUMO), and year (VAC2FLUYR) of their second most recent flu vaccination.
The 2010 NHIS sample includes variables associated with both versions of the flu vaccine questions. Beginning on August 11, 2010, the question no longer differentiates between seasonal flu and H1N1 flu vaccinations. The original NHIS files do not offer the variables associated with VACFLUYR for sample children in 2005-2009, or for sample adults in 2005-2015. IPUMS NHIS has utilized the vaccine-mode specific information to replicate VACFLUYR for sample children surveyed after August 10, 2010 and for sample adults in 2016 forward. Where sample persons reported receiving both a flu shot and a flu nasal spray vaccine in earlier samples with mode-specific questions, the most recent vaccination is used to populate the values in VACFLUYR. When sample persons have missing data for the date of vaccination for one mode, and valid data for the other mode (e.g., missing information for VACFLUSPYR and VACFLUSPMO with valid responses for VACFLUSHYR and VACFLUSHMO), the mode with valid date information is used to assign values to VACFLUMODE, VACFLUYR, and VACFLUMO.
Seasonal versus H1N1 flu vaccines
Generally, the survey question associated with this variable asks about seasonal flu vaccines and specifies that they are usually given in the fall to protect against influenza for the flu season. The 2009-2010 seasonal flu vaccine did not include protection against H1N1, as the H1N1 vaccine was developed later; from October 2009-August 10, 2010, the survey question explicitly clarifies that sample persons are NOT to include H1N1 or "swine" flu vaccines when answering this question. In January 2010, the NHIS added distinct supplemental questions about H1N1 flu vaccinations (VACH1N1GOT). Beginning on August 11, 2010 onward, the survey question clarifies that the sample person's most recent flu vaccination could have been the new 2010-2011 seasonal flu vaccine (which included protection against H1N1) or an H1N1 vaccine, but does not clarify which vaccination the sample person received.
The NHIS questionnaire was substantially redesigned in 2019 to introduce a different data collection structure and new content. For more information on changes in terminology, universes, and data collection methods beginning in 2019, please see the user note.
- 2005-2009: Sample adults age 18+ and sample children age 0-17 who had a flu shot or flu spray vaccine in the past 12 months.
- 2010-2010: All sample adults age 18+ and sample children age 0-17 interviewed prior to August 11, 2010 who had a flu shot or flu spray vaccine in the past 12 months; or sample children interviewed after August 10, 2010 who had a flu vaccine in the past 12 months.
- 2011-2015: Sample adults age 18+ who had a flu shot or flu spray vaccine in the past 12 months; or sample children age 0-17 who had a flu vaccine in the past 12 months.
- 2016-2018: Sample adults age 18+ and sample children age 0-17 who had a flu vaccine in the past 12 months.
- 2019-2021: Sample adults ages 18+ and sample children age 0-17 who have had at least one flu vaccine in the last 12 months and who gave the month or don't know the month of the vaccine dose.
- 2010-2021 : SAMPWEIGHT