The findings in this report are subject to at least two limitations. First, vaccination coverage was self-reported and therefore might be subject to inaccuracy. For those recalling a tetanus vaccination (within preceding 10 years), recall accuracy can be highly reliable, but unreliable for those not reporting one (sensitivity: 92.4%; specificity: 26.5%).8 Although the extent to which this was the case in this study is unknown, tetanus vaccination coverage likely was underestimated. The recall accuracy of Tdap vaccination, although unknown, likely is dependent on the provider-patient discussion of tetanus vaccination (including type) as well as patient comprehension and retention. However, the recollection period in this study spans at most 3 years, in contrast with at least 10 years for decennial tetanus boosters. Second, many respondents were excluded from estimations of Tdap coverage, creating a potential for bias, especially for underestimation of coverage; all respondents who reported a tetanus vaccination during 2005-2008, but were unable to say whether Td or Tdap was used, were excluded. This procedure yielded a coverage estimate of 5.9%. Actual Tdap coverage could fall within the range of 4.6% to 25.4%, depending on what proportion of excluded respondents actually received Tdap. Assuming that the excluded respondents received Tdap in the same proportion as did the respondents who knew which vaccine they received (52.1%), the coverage estimate would be 14.6%. Regardless, estimated Tdap vaccination coverage was suboptimal in 2008.