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Routine vaccinations and child survival: follow up study in Guinea-Bissau, West AfricaCommentary: an unexpected finding that needs confirmation or rejection

BMJ 2000; 321 doi: (Published 09 December 2000) Cite this as: BMJ 2000;321:1435

Rapid Response:

WHO response to Guinea-Bissau report

To the Editor,

The paper by Kristensen et al. in the December 9 issue of the BMJ (1)
challenges the safety of DTP, one of the principal vaccines used by
national immunization programmes. The authors shared their study results
with the World Health Organization prior to publication and they
cooperated in allowing a WHO review of the field sites in Guinea Bissau
and of the data bank in Copenhagen.

The Global Advisory Committee on Vaccine Safety of the WHO,
comprising an independent group of experts in drug safety, vaccine science
and epidemiology, which serves in an advisory capacity to the Department
of Vaccines and Biologicals of the WHO has given close consideration to
the reported findings and conclusions of the Kristensen paper. The
members of the committee have concluded that numerous and serious
deficiencies in the paper did not allow them to reach the same definitive
conclusions reached by the authors.

In particular, the reported observations are incomplete and do not
tally, no systematic effort has been made to address the likelihood of
bias introduced by the data collection method that was applied, and
categorical inferences have been drawn from data that are either not
statistically significant or are critically dependent on a very small
number of results that might equally be explained by chance. As well, the
probability of the results being distorted by confounding factors has not
been adequately addressed. The analysis was data driven and not based on
a priori generation of a hypothesis, which makes interpretation of
significance values and confidence limits problematic. The conclusions of
this paper need to be given the same level of scrutiny as adverse events
mistakenly attributed to DTP vaccine in the past.

The Vaccine Safety Advisory Committee is due to meet with the authors
on 21st December 2000 at WHO headquarters in Geneva to discuss the
committee’s concerns with the study and its conclusions.

It is important that the safety and impact of current immunization
schedules should be studied, particularly in high-risk situations. WHO
is committed to giving support to investigators, including to the authors
of the BMJ article, to conduct such work in a robust manner. We
emphasize that no change is warranted in current policy with regard to
immunization practices including BCG, DTP, oral polio and measles vaccines
in national immunization schedules.

PI Folb (chair)

on behalf of the WHO Global Advisory Committee on Vaccine Safety


1. Kristensen I, Aaby P, Jensen H. Routine vaccination and child
survival: follow up study in Guinea-Bissau, West Africa.. British Medical
Journal 2000;321:1435-1439.

Competing interests: No competing interests

08 December 2000
Peter I Folb
Professor of Pharmacology at UCT and Director of WHO Collaborating Center for Drug Policy,
University of Cape Town, RSA.