Background: Studies in West Africa and elsewhere have suggested that Bacillus Calmette-Guérin (BCG) vaccine given at birth is beneficial for child survival. It is possible that this effect is mediated partly through an effect on malaria, a hypothesis supported by animal studies. We investigated whether revaccination with BCG at 19 months of age reduced morbidity from malaria.
Method: In the capital of Guinea-Bissau, between January and November 2003, children who had previously received BCG vaccination and who did not have a strong reaction to tuberculin were individually randomised to either receive revaccination with BCG at the age of 19 months or to be a control. Episodes of malaria were recorded during the 2003 malaria transmission season through passive case detection at health centres in the study area and at the national hospital. Cross-sectional surveys were carried out at the beginning and at the end of the rainy season.
Results: Incidence rates of first episodes of malaria associated with any level of parasitaemia were 0.16 episodes per child-year among 713 revaccinated children and 0.12 among 720 control children [incidence rate ratio (IRR) = 1.37; 95% confidence intervals (CI): 0.84-2.25]. Results were similar when the diagnosis of malaria was based on the presence of parasitaemia >5000 parasites/microl (IRR = 1.30; 95% CI: 0.61-2.77). The incidence of all-cause hospitalisation was higher among BCG-revaccinated children than among controls (IRR = 2.13; 95% CI: 1.10-4.13). There were no significant differences in the prevalence of parasitaemia between the two groups of children at cross-sectional surveys.
Conclusion: We found no evidence that BCG revaccination reduces morbidity from malaria.