Many studies demonstrate that routine Expanded Program on Immunisation (EPI) vaccinations have "non-specific" or "heterologous" effects on child survival that cannot be accounted for by protection against the vaccine specific disease. These effects were overlooked in the past because it was assumed that the impact on survival would be proportional to reduction in the targeted infection. Large epidemiological studies in Bangladesh and Guinea-Bissau have shown that live vaccines, including measles vaccine (MV), have beneficial effects on overall mortality which cannot be explained by protection against the vaccine specific disease. Deleterious non-specific effects were shown convincingly in the high-titre MV trials in which girls, but not boys, had a two-fold increase in mortality even though the vaccine was fully protective against measles. A reinterpretation of these trials indicated that the most likely explanation was that the increased female mortality was due to inactivated vaccines provided after MV. It has further been shown in smaller observational studies that receiving diphtheria, tetanus and whole cell pertussis combined vaccine (DTwP) either with or after MV negates the beneficial effects of MV, and may lead to increased mortality. However, the increased mortality of girls in male-female twin pairs was not apparent when MV was given after the last dose of DTwP. In the present EPI schedule in The Gambia, DTwP is administered as a single dose vaccine at 2, 3 and 4 months, and MV at nine months. However, many children, particularly in low income countries, present late for their vaccines and may subsequently receive them in the wrong order. In particular DTP is often given at the wrong time point, e.g. the third DTP dose (DTP3) with MV. Given the increasing evidence that the order in which vaccines are administered is crucial, the routine practice of administering missed EPI vaccines at late presentation or boosting with DTP in year 2 may not be advisable.