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.