A randomized controlled trial of acellular
diphtheria/
pertussis/
tetanus (ADPT) freeze-dried and liquid
vaccines in infants was conducted in a peri-urban community (Ashaiman) in southern Ghana. Immunogenicity of the
acellular vaccines, persistence of
antibodies and adverse reactions were compared with those achieved with a whole-cell
diphtheria-
pertussis-
tetanus (
DPT) vaccine. The incidence of
pertussis in the
vaccine groups and prevalence of
pertussis in children under 5 years of age in the study area were also determined. The
acellular vaccines produced significantly fewer local and systemic reactions. Local reactions such as swelling and redness were observed in 2% (8/399) to 2.3% (9/385) of the
acellular vaccine recipients as against 31% (122/394) in the whole-cell
vaccine group.
Fever ( > or = 37.5 degrees C) occurred in 7.27% (29/399) to 9.8% (38/385) in the
acellular vaccine groups compared with 36.6% (145/394) in the whole-cell
vaccine group. Geometric mean titres (GMTs), measured by ELISA, to
pertussis toxin (PT) and filamentous haemagglutinin (FHA) were significantly higher in the
acellular vaccine groups than in the whole-cell DPT (WCDPT) group. There were no significant differences in the GMTs of
tetanus and
diphtheria antitoxins between the two groups after each vaccination. Twelve months after primary vaccination, GMTs to PT in the freeze-dried, liquid ADPT groups and the WCDPT group have fallen from 56.23, 62.63 and 44.97 ELISA U/ml to 6.08, 6.18 and 11.30 ELISA U/ml, respectively. GMTs to FHA in all the
vaccine groups also dropped during the same period from 49.94, 41.73 and 20.74 ELISA U/ml to 7.26, 7.72 and 5.91 ELISA U/ml, respectively. In this comparative controlled trial, the ADPT
vaccines were more immunogenic, with less local and systemic reactions, than the WCDPT
vaccine but there was a considerable drop in antibody titres in all the
vaccine groups 12 months after primary vaccination. However, the levels of titres of anti-PT and anti-FHA
antibodies in all the three
vaccines that confer protection are not known. Further studies are necessary to provide this information in order to assess the need for subsequent booster doses after primary immunization with both ADPT and WCDPT
vaccines.