The effect of OPV is difficult to separate from the effects of BCG and DTP vaccines since OPV is normally given together with these vaccines. There have, though, been some periods without DTP in Bissau due to global shortage of vaccines, and we have compared the case fatality at the hospital for children who received only OPV and children who received both the prescribed OPV and DTP. Children having received OPV had 3-fold lower mortality than children having received both vaccines. Data from an OPV vaccination campaign that took place in Guinea-Bissau also suggested a non-specific beneficial effect for the recipients. Further, studies from Chile and the Soviet Union have suggested that OPV had a beneficial effect on mortality and morbidity.