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Acellular pertussis vaccines: the rationale for an efficacy trial in Germany
H J Schmitt1, A Schuind, M Knuf
1Children's Hospital, Christian-Albrechts-University zu Kiel, Germany.
Insights
A new diphtheria-tetanus toxoid-acellular pertussis (DTPa) vaccine demonstrated 89% efficacy in preventing pertussis. This study assessed DTPa vaccine effectiveness in Germany following concerns about whole-cell pertussis vaccines.
Area of Science:
- Immunology
- Vaccinology
- Pediatric infectious diseases
Background:
- Withdrawal of whole-cell pertussis vaccines (DTPw) in Germany in 1974 led to a significant rise in pertussis cases.
- Despite the reintroduction of vaccination recommendations in 1991, DTPw vaccine uptake remained low.
- The German healthcare system facilitates regular pediatrician-pediatrician contact, enabling large-scale vaccine efficacy studies.
Purpose of the Study:
- To evaluate the efficacy of the diphtheria-tetanus toxoid-acellular pertussis (DTPa) vaccine.
- To address the public health need for effective pertussis prevention following safety concerns with DTPw vaccines.
Main Methods:
- A prospective household contact study with blinded clinical follow-up was conducted, as a placebo-controlled trial was not ethically feasible.
- Pediatricians screened potential participants and initiated diagnostic procedures.
- Independent, blinded physicians performed clinical follow-up to ensure unbiased assessment.
Main Results:
- The DTPa vaccine demonstrated a calculated efficacy of 89% (95% confidence interval, 76.6%-94.6%).
- No identified confounding factors were found to bias the results in favor of the DTPa vaccine.
Conclusions:
- The diphtheria-tetanus toxoid-acellular pertussis (DTPa) vaccine is highly effective in preventing pertussis.
- These findings support the use of DTPa vaccines for pertussis control in pediatric populations.
Abstract:
After concern about the safety of diphtheria-tetanus toxoid-whole cell pertussis vaccines (DTPw), the recommendation to vaccinate children with DTPw was withdrawn in 1974 in the former West Germany. This led pertussis cases to increase to an estimated 100,000 annually. Despite renewal of the vaccination recommendation in 1991, vaccine use remained low. The German health care structure assures regular contact between most children and pediatricians. This enabled the conduct of a large efficacy trial with a diphtheria-tetanus toxoid-acellular pertussis (DTPa) vaccine. Because a placebo-controlled trial was not ethically possible, a prospective household contact study with a blinded clinical follow-up was done. Possible study participants were screened by their pediatrician, who also initiated diagnostic procedures. Clinical follow-up was done by another locally based but independent and blinded physician. Vaccine efficacy was calculated to be 89% (95% confidence interval, 76.6%-94.6%). None of the identified confounding factors biased results in favor of the DTPa vaccine.