Live vaccines, such as oral poliovirus vaccine; yellow fever vaccine; and measles, mumps and rubella vaccines, do not contain thiomersal, because it would kill the immunizing component.

We also administered a challenge dose of monovalent type 1 oral poliovirus vaccine at 7 months and collected stool samples before and 7 days after administration of the challenge dose.

In the meantime, more than 33 000 children were paralysed by wild poliovirus while more than 6.5 million polio cases were prevented by the oral polio vaccine.