Monocomponent Pertussis Toxoid Vaccine Immunologic and Epidemiologic Experience of Vaccination With a

ABSTRACT. Pertussis re-emerged in Sweden with acumulative incidence of about 60% during the first 10years of life, when the locally produced cellular vaccinelost its efficacy around 1970 and general vaccination wasdiscontinued in 1979. The epidemiology, clinical fea-tures, and immunology of pertussis and a monocompo-nent pertussis toxoid vaccine were studied in Go¨teborg,Sweden.After phase 1 and 2 studies, a randomized, double-blind, placebo-controlled trial of pertussis toxoid (P Tox ),compounded with diphtheria and tetanus toxoids, wasadministered to 3450 children according to the Swedishschedule at 3, 5, and 12 months of age. After a meanfollow-up of 18 months, the efficacy was 71% overall and75% in household contacts, respectively. A statisticallysignificant correlation was found between the level ofP Tox- induced antibodies and protection against pertus-sis. As observed with cellular and with multicomponentacellular vaccines, P Tox reduced the severity of diseaseand the percent of children with positive cultures. Fur-thermore, vaccination reduced the transmission of