Household characteristics and the distributions of households with influenza introduced^a and transmission documented^b: the Household Influenza Vaccine Effectiveness (HIVE) study, Ann Arbor Michigan, 2010-2011 influenza season.

*P-value < 0.05 from Chi-square test for independence of outcome across categories. aAt least one household index case with community-acquired influenza. bAt least one secondary case of influenza resulting from exposure to a household index case. cThe percent values presented are column percentages that add to 100 for each household characteristic. dThe percent values presented are row percentages with the corresponding cell in the All Households column as the denominator. eData missing for 24 households (3 with introduction of influenza, 1 of which resulted in secondary transmission).