Vaccination and child mortality

Abstract

A report in 2000 from Guinea Bissau suggested a worrisome association between diphtheria pertussis and tetanus (DPT) vaccination and mortality. In this issue of The Lancet Robert Breiman and colleagues respond to concerns about DPT with a highly detailed and reassuring study of vaccination and mortality in Bangladesh. At an epidemiology conference in Helsinki in 1989 Peter Aaby and I spent a few days discussing a problem: vaccines are usually introduced into developing countries with no assessment of their potential effect on overall mortality. The key issue is that if trials of vaccines are to show a beneficial effect or at least that they cause no harm the trials need to be so large that they are difficult to fund. Another problem is that once a vaccine has been shown to reduce the frequency of the target disease it becomes ethically questionable to have an unvaccinated group. Aaby tried to address this issue by using observational data from demographic surveillance in Guinea Bissau. He has published papers suggesting unexpected associations between vaccine use and later patterns of mortality. His findings on DPT vaccine prompted WHO to look closely at his data (including a site visit by independent experts) to commission studies around the world where the association could be studied and then to hold a meeting of experts to review and report all data in WHO’s Weekly Epidemiological Record. (excerpt)