The chemicals contained vaccines are not in a toxic form. Vaccine production is constantly being refined to reduce any potential side-effects.
While some vaccinations, including the common flu shot, do contain mercury in a preservative known as thimerosal, the mercury is in a compound called ethylmercury. Unlike methylmercury, the body can eliminate this compound quickly without any lasting effects.
The aluminium present in some vaccines is present in aluminium salts designed to elicit a stronger immune response. However, the quantities of aluminium in these salts is so small that it does not pose a risk to the child.