<P> Some researchers have been selectively reporting results of studies on non-specific effects of DTP vaccines, bringing about the question of whether there is type 1 error affecting these reports (see paragraphs below). A systematic review was recently completed on this topic so as to compile and rate all of the available evidence . This review showed that receipt of DTP had no significant non-specific effect on all - cause mortality (relative risk 1.38, 0.92 to 2.08). In addition, it showed that many of the studies reporting on this topic were at a high risk of bias . The WHO has recommended that further studies, which are well designed and reflect current vaccine schedules, be carried out on this topic . </P> <P> DTP vaccine seem to have negative non-specific effects other than the beneficial effect against the targeted disease . The negative effects are seen as long as DTP vaccine is the most recent vaccine . BCG or measles vaccine given after DTP reverses the negative effects of DTP . The negative effects are seen mostly in females . </P> <P> The negative effects are found in several observational studies . However, six WHO - commissioned studies concluded that there were strong beneficial effects of DTP on overall mortality . However, controversy ensued as to the design of these studies that had important methodological shortcomings . Among others, the WHO - commissioned studies had counted "no information about vaccination" as "unvaccinated", and they had retrospectively updated vaccine information from surviving children, while no similar update could be made for dead children, creating a so - called "survival bias" which will always produce highly beneficial effect estimates for the most recent vaccine . </P>

When was whooping cough vaccine added to tetanus