Effect of diphtheria–tetanus–pertussis (DTP) vaccination on child survival
This issue has been the subject of previous deliberations and review by GACVS.1 At its December 2003 meeting,2 GACVS commissioned a special task force, independent of the Committee, to review the evidence for a deleterious effect (if any) of DTP vaccination on child survival. The terms of reference of the task force were to determine whether, from published work and any other sources known to the task force, evidence exists to support a nonspecific increased mortality in infants caused by DTP vaccination in the first year of life. On the basis of its findings and conclusions, the task force was charged to advise: (i) whether WHO should recommend changes in vaccination policies, with particular reference to DTP vaccination; and (ii) what further work, if any, might be done to resolve the matter.
The review group considered published papers, and unpublished work that had been supplied to WHO by the authors, relevant to the hypothesis that DTP vaccination might adversely influence subsequent child mortality. The group considered seven papers from the group involved with the study in Guinea-Bissau, published in the British Medical Journal in 2000, in which a deleterious effect of DTP on child survival had been postulated, nine papers from other investigators in other countries and one review article.
Members were unanimous that the totality of evidence provided in all the material before the task force did not support a deleterious effect of DTP vaccination on child survival; indeed, the papers provide substantial evidence against such a conclusion. The task force also concluded that the potential effects of DTP and OPV cannot be distinguished when the two vaccines are given together, as happened in the majority of settings.
Advised by the report of the task force, GACVS decided to regard the issue of a deleterious effect on childhood survival of DTP vaccination as not supported by the evidence and to set the matter aside unless new and persuasive evidence were to emerge in the future. GACVS restated the importance of keeping an open mind on the unexpected outcomes of immunization and of the necessity of doing so through a comprehensive system of signal generation, collation of evidence and review of causality. The Committee stressed the importance of evaluating signals through rigorous studies responding to a priori research and clinical questions.
The Committee will keep a watching brief on any evidence suggesting other nonspecific effects of vaccination.
- See WER No. 47, 2002, pp. 389–394 and No. 32, 2003, pp. 282–284.
- See WER No. 3, 2004, pp. 16–20.