The findings in this report are subject to at least six limitations. First, the BRFSS is a landline telephone survey, and therefore subject to selection bias because of noninclusion of cell-phone–only households and households with no telephone service. Second, nonresponse bias might remain after weighting adjustments. Third, the vaccination coverage estimates reported here are based on data from 19 states. Consequently, those estimates might not be representative of the entire U.S. population. However, seasonal influenza vaccination coverage estimates among adults in the 19 states were similar to those for the 46 states and District of Columbia (within 0.2-2.7 points, depending on the age group), and to the NHIS results.5 Fourth, influenza vaccination status was based on self-report, which might result in under- or overreporting because of recall or social desirability bias. Fifth, this survey collected coverage status only through December, although vaccinations continued through March, this underestimates vaccination coverage. However, a comparison using 2008 BRFSS data found that, based on interviews primarily from January and February, coverage among adults was no more than 4 percentage points lower than coverage based on March through August interviews (CDC, unpublished data, 2009). Finally, the BRFSS question about child influenza vaccination asks for the date of the most recent flu vaccination received during the 12 months before the day of the interview; consequently, full vaccination status among children aged 6 months–8 years, who require 2 vaccine doses in their first season to be vaccinated fully, could not be determined.