Efficacy of acellular pertussis vaccine

Abstract

An outbreak of pertussis occurred in one room of a residential facility where 19 children aged 5 to 36 months were residing. They were prospectively surveyed to estimate the efficacy of acellular pertussis vaccine. Among the 19 residents, 9 were immunized with acellular pertussis vaccine. Among the 19 residents, 9 were immunized with acellular DTP vaccine and 10 were unimmunized. The spread of pertussis was surveyed bacteriologically and serologically for 2 months. Among the 9 immunized, 7 children acquired the laboratory-confirmed pertussis and 1 of the 7 developed the typical symptoms (whooping or paroxysmal coughing attack lasting for 14 days or more). Among the 10 unimmunized, 7 children acquired the laboratory-confirmed pertussis and 6 of the 7 developed the typical symptoms. There was no difference in the rate of secondary infection (7/9:7/10), but there was a significant difference in the rate of development of the typical symptoms (1/7:6/7 p less than 0.05). The point estimate of protective efficacy of the acellular DTP vaccine against typical pertussis was (6/10 - 1/9)/(6/10) x 100 = 81%. It was concluded from these findings that acellular DTP vaccine could not prevent the infection of Bordetella pertussis, but could prevent the development of the typical symptoms.