Low levels of antipertussis antibodies plus lack of history of pertussis correlate with susceptibility after household exposure to Bordetella pertussis.

Prospectively collected data in a Swedish vaccine efficacy trial were used to investigate transmission of pertussis from small study infants to other household members. Forty one percent (258/627) of the exposed persons with paired serology had laboratory confirmed pertussis. The majority of those with laboratory confirmed pertussis had less than 14 days of cough and many were asymptomatic. High susceptibility to symptomatic pertussis was found among persons with low initial IgG antibody concentrations against pertussis toxin, especially those without previous history of pertussis vaccination or disease.