We previously compared the effect on mortality of the half dose and the full dose currently recommended by WHO. Unexpectedly, the low dose was clearly better for girls, but not for boys. The girls' response might have depended on the last vaccine received before the OPV and VAS campaign. We believe that these findings call for confirmation. In connection with a new campaign, we will examine whether half the dose or the full dose has a more beneficial effect on mortality and morbidity in girls, and furthermore address the potential effect modification by the last vaccine received before the supplementation.

In Guinea-Bissau, a combined OPV and VAS campaign took place in November 2002. Given the uncertainty about the best dose of VAS, we examined whether the half dose compared with the full dose currently recommended by WHO gave an equally good protection against childhood morbidity and mortality. Mortality after supplementation was lower, though not significantly so, for children who had received the half dose. However, there was a highly significant inversion of the effect for boys and girls; while the low dose was clearly better for girls, the full dose might have been slightly better for boys. The girls' responses to the high versus the low dose of vitamin A might have depended on the last vaccine received before the OPV and VAS campaign.

We believe that these findings call for confirmation. In connection with the OPV and VAS campaign in November 2004 in Guinea-Bissau, we intend to examined whether half the dose of the dose currently recommended by WHO as compared to the full dose has a more beneficial effect on mortality and morbidity in girls, and furthermore address the potential effect modification by the last vaccine received before the supplementation.

Inclusion Criteria:Between 6 mo and 5 years of age and thus eligible for vitamin A and OPV campaign -

Exclusion Criteria:Overt signs of vitamin A deficiency

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