Concerns about the safety of whole-cell
pertussis vaccines prompted development of
acellular vaccines that are less likely to provoke adverse events because they contain purified antigenic components of Bordetella pertussis. Two
diphtheria and
tetanus toxoids and acellular
pertussis (
DTaP) vaccines--
ACEL-IMUNE and
Tripedia--have been licensed for several years, but (until recently) only for administration of the fourth and fifth doses in the series to children aged 15 months-6 years who previously had received three or more doses of
diphtheria and
tetanus toxoids and whole-cell
pertussis (
DTP) vaccine. Published reports indicate that, when administered to infants aged 2, 4, and 6 months, acellular
pertussis vaccines are effective in preventing
pertussis disease and associated with fewer local, systemic, and certain more serious adverse events than whole-cell
pertussis vaccines. On the basis of these data, the Food and Drug Administration (FDA) has licensed three
DTaP vaccines for use among children aged 6 weeks-6 years.
Tripedia is now licensed for the initial four doses, and
ACEL-IMUNE for all five doses of the
diphtheria,
tetanus and
pertussis vaccination series. A third
DtaP vaccine (Infanix) was licensed in January 1997 for the initial four doses of the series.
Tripedia,
ACEL-IMUNE, and Infanix are now recommended for routine vaccination of infants and young children, although whole-cell
pertussis vaccines remain acceptable alternatives.
Tripedia,
ACEL-IMUNE, and Infanix are recommended for all remaining doses in the schedule for children who have started the vaccination series with one, two, three, or four doses of whole-cell
pertussis vaccines. In September 1996, FDA licensed the use of
TriHIBit (
ActHIB reconstituted with
Tripedia) for the fourth dose in the series of vaccinations against
diphtheria,
tetanus,
pertussis, and Haemophilus influenzae type b disease.