Codes and Frequencies
For sample children who had a two or more flu vaccines in the past 12 months, VAC2FLUMO reports the month of the child's second most recent flu vaccine. For the corresponding year of the child's second most recent flu vaccine, see VAC2FLUYR.
See the Comparability Tab for additional information about using this variable in the 2010 sample as well as information about seasonal flu versus H1N1 flu vaccinations in 2010-2011.
Comparability is affected by changes to the universe and the 2019 redesign. Because of a change to the flu vaccine questions, the 2010 NHIS sample for this variable only includes sample children interviewed after August 10, 2010 who had two or more flu vaccines in the past 12 months. In 2011-forward, all sample children who had two or more flu vaccines in the past year are included in the universe of this variable.
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.
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 original NHIS files do not offer the variables associated with VAC2FLUMODE for sample children in 2005-2009, or for sample children surveyed before August 11, 2010. The 2010 NHIS sample includes variables associated with both versions of the flu vaccine questions.
When first introduced, 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.
- 2010: Sample children age 0-17 interviewed before August 11, 2010 who reported having both a flu shot vaccine and a flu spray vaccine, OR sample children interviewed after August 10, 2010 who had more than one flu vaccine in the past 12 months.
- 2011-2018: Sample children age 0-17 who had more than one flu vaccine in the past 12 months.
- 2019-2022: Sample children age 0-17 who had more than one flu vaccine in the past 12 months.
- 2010-2022 : SAMPWEIGHT