Tetanus, Diphtheria and Pertusis (Tdap) is indicated as a booster immunization as a single dose in persons over 10 years of age.⁷ Family members are the primary source of pertussis in infants. Studies show that when the source can be identified, family members are the source in up to 83% of cases transmitted to infants.⁷ Infants under 6 months of age are most vulnerable to complications from pertussis.⁷