Implementation and assessment of vaccination programmes: the importance of vaccination sequence for overall health outcomes.

In addition to their effect on the target infections, accumulating evidence indicates that vaccines have non-specific effects. Live measles vaccine (MV) has beneficial NSEs reducing mortality by more than can be explained by preventing measles infection. In contrast, non-live diphtheria-tetanus-pertussis vaccine (DTP) has negative NSEs; in spite of protecting against diphtheria, tetanus and pertussis, it is associated with increased mortality. The most recent vaccine has the strongest effect on child health, and therefore sequence of vaccines is important. There is consistent evidence that DTP with or after MV is associated with increased mortality compared with having MV as the most recent vaccine, but the sequence of vaccines is not considered in the current evaluation and implementation of vaccination programmes. To maximise the impact of current vaccination programmes on child health, increased emphasis should be placed on receiving MV after DTP. Increasing time with live MV as the most recent vaccine through better adherence to the schedule, and modified recommendations for catch-up vaccinations for children who do not follow the recommended schedule are likely to result in improvements in child health.