From 1995 to 2002, all children in the BHP study area were included in an early two-dose measles vaccination trial from 6 months of age. The children were randomised to either a one-dose group receiving an inactivated polio vaccine (IPV) at 6 months of age and a measles vaccine at 9 months of age, or a two-dose group receiving two doses of measles vaccine at 6 and 9 months of age. For the first 6 months of the trial, the standard-titre EZ measles vaccine was used, for the rest of the trial the standard-titre SW vaccine was used. Results from the trial showed that an early two-dose schedule increased coverage considerably and provided better protection against measles among infants than the recommended one-dose at 9 months of age schedule. The EZ and the SW vaccine were used in two different cohorts - so a direct comparison was not possible, but the EZ vaccine seemed to boost a secondary immune response better than the SW vaccine. Further, the SW vaccine was less able to induce a protective level of antibodies when used from 6 months of age than the EZ vaccine. The preliminary data that we have on long-term vaccine efficacy supports that the SW vaccine might be less suitable than the EZ vaccine for use in very early measles vaccine schedules (unpublished data). On the other hand, trials performed during the 1980's in Mexico and Bangladesh have shown that administration of the standard-titre EZ vaccine to infants as young as 4-6 months of age gave good seroconversion results.