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Randomized controlled trial of acellular diphtheria, pertussis and tetanus vaccines in southern Ghana
E A Afari1, Y Kamiya, F K Nkrumah
1Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
Insights
Acellular diphtheria/pertussis/tetanus (ADPT) vaccines showed better immunogenicity and fewer reactions than whole-cell DPT vaccines in Ghanaian infants. However, antibody levels dropped significantly after 12 months, necessitating further research on booster doses.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Immunology
Background:
- Whole-cell diphtheria-pertussis-tetanus (WCDPT) vaccines are associated with significant local and systemic reactions in infants.
- Acellular diphtheria/pertussis/tetanus (ADPT) vaccines offer a potentially safer alternative with comparable or improved immunogenicity.
- Understanding vaccine efficacy and antibody persistence is crucial for optimizing infant immunization schedules.
Purpose of the Study:
- To compare the immunogenicity, antibody persistence, and adverse reactions of freeze-dried and liquid ADPT vaccines versus WCDPT vaccine in Ghanaian infants.
- To determine the incidence of pertussis in vaccine recipients and the prevalence of pertussis in the study area.
- To evaluate the need for booster doses by assessing antibody levels 12 months post-primary vaccination.
Main Methods:
- A randomized controlled trial involving infants in a peri-urban community in southern Ghana.
- Comparison of immunogenicity (ELISA for anti-pertussis toxin [PT] and filamentous haemagglutinin [FHA], tetanus, and diphtheria antitoxins) and adverse reactions.
- Monitoring of pertussis incidence and prevalence in children under 5 years.
Main Results:
- ADPT vaccines elicited significantly higher geometric mean titres (GMTs) for PT and FHA compared to WCDPT.
- ADPT recipients experienced substantially fewer local reactions (2-2.3%) and fever (7.3-9.8%) than WCDPT recipients (31% and 36.6%, respectively).
- Antibody titres (GMTs) for PT and FHA declined significantly in all vaccine groups 12 months after primary vaccination.
Conclusions:
- ADPT vaccines are more immunogenic and safer than WCDPT vaccines in infants.
- A significant drop in antibody titres 12 months post-vaccination suggests potential waning immunity.
- Further studies are required to determine protective antibody levels and inform booster dose recommendations for both ADPT and WCDPT vaccines.
Abstract:
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.