Vaccination and child survival in the developing world: lessons from the Guinea Bissau studies
The paper by Kristensen et al. in the current edition of the BMJ (1)
describes improved survival in Guinea Bissau infants who received measles
or BCG vaccines, but increased mortality in those who received DTP
vaccine. At the request of WHO we visited Guinea Bissau between October 8
and 15, 2000 to review this study. We found the methodology for the study
to be as it is described in the paper. As data collection is continuing,
we were able to accompany the field staff on several visits.
the data management procedures and found them to be in order. While
several potential source of bias could be hypothesised we were not able to
identify any one that could invalidate the study. This is a single study,
which was not originally designed to address this issue, and there are
methodological weaknesses that have been highlighted in the accompanying
editorial and commentary. By its characteristics and its surprising
findings it should provoke substantial further investigation of the
subject. While these result should not be used as a basis for changing
national or global vaccination policy, this is a matter for concern
demanding an immediate response. The first response it to seek out data
from other developing countries that may be used to address this question.
It is possible that other studies may not show the same findings in
relation to DTP, in which case the particular circumstances of Guinea-
Bissau should be considered. In that country, at the time of the study, 25
-30% of all children died before their 5th birthday, most from malaria or
pneumonia although this has not been well studied. Of particular interest
therefore will be the analysis of data from other high mortality settings
with intense malaria transmission.
Regardless of the outcome of the ongoing investigations, the work of
in Guinea-Bissau highlights the importance of considering the overall
impact of vaccines on children's health. In that respect the finding that
measles and BCG appear to improve survival beyond what can be attributed
to the prevention of those specific diseases is particularly good news
that should stimulate similar studies in other areas.
There are broader lessons to be learned from the publication of this
study. Public health research to support public health interventions is
not a luxury, but a necessity. The overall impact of routine childhood
vaccines on survival in high mortality settings has not been evaluated
systematically. We should learn from this omission and ensure that in the
future all public health interventions are underpinned by the appropriate
public health experimental and observational research to ensure that they
are both safe and efficacious.
Dr. Kim Mulholland, Professor, Department of Paediatrics, University of
Melbourne, Australia.(email email@example.com)
Dr. Mauricio L. Barreto, Professor, Instituto de Saude Coletiva, Federal
University of Bahia, Salvador-Bahia Brazil (email: firstname.lastname@example.org).
1. Kristensen I, Aaby P, Jensen H. Routine vaccination and child
survival: follow up study in Guinea-Bissau, West Africa.. British Medical
Competing interests: No competing interests