Thiomersal in vaccines - Is removal warranted?

The mercury-based vaccine preservative thiomersal has come under scrutiny i n recent months because of its presence in certain vaccines that provide th e foundation of childhood immunisation schedules. Over the past decade new vaccines have been added to the recommended childhood schedule, and the rel atively smaller bodyweight of infants has led to concern that the cumulativ e exposure of mercury from infant vaccines may exceed certain guidelines fo r the human consumption of mercury. In the US, government agencies and prof essional societies have recently recommended that thiomersal be removed alt ogether from vaccines. Some involved in developing vaccine policy feel that the evidence to support these safety concerns has not risen to the level r equired for such a response. This apparent divergence of opinion has left h ealthcare professionals and the public with uncertainty about the potential health effects from low level exposure to thiomersal as well as the necess ity of removing thiomersal from vaccines. At present, scientific investigat ion has not found conclusive evidence of harm from thiomersal in vaccines. As a precautionary measure, efforts are under way to remove or replace thio mersal from vaccines and providers should anticipate the availability of mo re vaccine products that are thiomersal-free over the coming years.