Elsevier

Vaccine

Volume 22, Issues 23–24, 13 August 2004, Pages 3014-3017
Vaccine

Oral polio vaccination and low case fatality at the paediatric ward in Bissau, Guinea-Bissau

https://doi.org/10.1016/j.vaccine.2004.02.009Get rights and content

Abstract

Oral polio vaccine (OPV) and diphtheria–tetanus–pertussis (DTP) vaccines are given simultaneously in routine immunisation programmes in developing countries. It is therefore difficult to determine the separate effects of these vaccines on survival. We used the shortage of DTP vaccine in Bissau to examine the impact of OPV on the case fatality at the paediatric ward in Bissau. For 719 children less than 5 years of age whose vaccination card had been seen at admission and who had not yet received measles vaccine, having received OPV only was associated with a case fatality of 6% compared with 15% for children having received combined DTP and OPV vaccinations, the case fatality ratio (CFR) being 0.29 (95% confidence interval (CI) 0.11–0.77). Even if children fleeing the hospital were assumed to have died shortly after leaving the hospital, the case fatality would still be lower for children having received OPV only (CFR=0.41 (95% CI 0.20–0.81)). The tendency was similar for children hospitalised with pneumonia, diarrhoea, and presumptive malaria. Control for background factors had no impact on the estimate. In areas with high mortality, OPV administered alone may have non-specific beneficial effects or DTP may have a negative effect for children who had received both DTP and OPV.

Introduction

In areas with high child mortality, routine immunisations may have important non-specific effects on survival [1], [2], [3], [4], [5], [6]. For example, high-titre measles vaccine was protective against measles infection but associated with increased mortality when compared with standard measles vaccine [3]. Effects have been markedly positive when BCG, often given with oral polio vaccine (OPV), or measles vaccine was the last vaccine received [1], [2], [4]. However, in several studies from West Africa, diphtheria–tetanus–pertussis (DTP) and OPV vaccines have not been associated with reduced mortality [1], [2], [4], [5], [6]. Since DTP and OPV vaccines are usually administered together, it is difficult to distinguish the separate effects of these vaccines. Recently, the provision of DTP has been irregular in Guinea-Bissau. We therefore used the occasional shortage of DTP in Bissau city to assess the separate impact of OPV on the case fatality at the paediatric ward.

Section snippets

Subjects and methods

From May 2001 to April 2002, we registered all children hospitalised at the only paediatric ward in Bissau to examine the possible impact of immunisation status on the in-hospital case fatality. The recommended vaccination schedule in Bissau is BCG and OPV at birth and simultaneous doses of DTP and OPV at 6, 10, and 14 weeks of age, and finally measles vaccine at 9 months of age. During the present study, DTP was missing from the local health centres during May–June and August–September 2001,

Results

Among the 2126 children who had their vaccination card inspected, 719 had received either OPV only or DTP and OPV and no measles vaccine yet, the case fatality being 14% (102/719). Controlling for age, children who had received OPV only had a CFR of 0.29 (95% CI 0.11–0.77) compared with the children who had received both DTP1 and OPV (Table 1). Controlling for both age and number of vaccination doses, children who had received OPV only had a CFR of 0.29 (95% CI 0.11–0.77) compared with the

Discussion

When oral polio was introduced in the 1960s, a Chilean study observed a significant reduction in mortality and suggested that the effect could be due to OPV virus limiting the replication of other enterovirus [7]. In randomised studies conducted in the Soviet Union in the 1950s and 1960s, Voroshilova found a marked reduction in gastrointestinal and respiratory morbidity associated with the use of non-pathogenic enterovirus vaccines including OPV [8]. Following national polio immunisation days

Acknowledgements

Contributors: A.R. and P.A. planned the study in collaboration with S.B., C.M. and J.E.V. who established the hospital register. A.R., H.J., C.B. and P.A. planned the analyses. P.A. wrote the first version of the paper, and all authors contributed to the final version. Conflict of interest statement: None declared. Funding: Research was funded from The Council for Development Research, Denmark, and the EU Commission (IC18CT95-0011). P.A. holds a research professorship funded by the Novo Nordisk

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