A CONTROLLED TRIAL OF A 2-COMPONENT ACELLULAR, A 5-COMPONENT ACELLULAR, AND A WHOLE-CELL PERTUSSIS-VACCINE

Background. Because of concern about safety and efficacy, no pertussis vaccine has been included in the vaccination program in Sweden since 1979, To provide data that might permit the reintroduction of a pertus sis vaccine, we conducted a placebo-controlled trial of two acellular and one whole-cell pertussis vaccines. Methods. After informed consent was obtained, 9829 children born in 1992 were randomly assigned to re ceive one of four vaccines: a two-component acellular diphtheria-tetan us-pertussis (DTP) vaccine (2566 children), a five-component acellular DTP vaccine (2587 children), a whole-cell DTP vaccine licensed in the United States (2102 children), or (as a control) a vaccine containing diphtheria and tetanus toxoids (DT) alone (2574 children). The vaccin es were given at 2, 4, and 6 months of age, and the children were then followed for signs of pertussis for an additional 2 years (to a mean age of 2 1/2 years). Results. The whole-cell vaccine was associated wi th significantly higher rates of protracted crying, cyanosis, fever, a nd local reactions than the other three vaccines. The rates of adverse events were similar for the acellular vaccines and the control DT vac cine. After three doses, the efficacy of the vaccines with respect to pertussis linked to a laboratory-confirmed case of pertussis or contac t with an infected household member with paroxysmal cough for greater than or equal to 21 days was 58.9 percent for the two-component vaccin e (95 percent confidence interval, 50.9 to 65.9 percent), 85.2 percent for the five-component vaccine (95 percent confidence interval, 80.6 to 88.8 percent), and 48.3 percent for the whole-cell vaccine (95 perc ent confidence interval, 37.0 to 57.6 percent). Conclusions. The five- component acellular pertussis vaccine we evaluated can be recommended for general use, since it has a favorable safety profile and confers s ustained protection against pertussis. The two-component acellular vac cine and the whole-cell vaccine were less efficacious.