Last year, some Missouri children got flu vaccines containing a mercury compound called thymersol.

This year one department is making sure that doesn't happen again. A law that took effect last April requires mercury-free vaccines for children younger than three - and for women who are pregnant.

A recent state audit says the Department of Health and Senior Services failed to tell the public and medical providers about the new law.

"What happened in 2007, last year, is that many providers didn't know about the law and ordered just regular flu vaccines and didn't order the type of flu vaccine that does not contain thymersol in it," according to Nanci Gonder of Missouri Health and Senior Services. "There were concerns that our department hadn't done enough to make sure that providers knew about the law."

Because not all flu shot providers knew about the new law, some Missouri children got vaccines with mercury. So this year, the department made sure medical providers knew of the change.

"After last year we made more effort and others made more effort to make sure providers knew about this law," Gonder said.

The Columbia/Boone County Department of Public Health and Human Services knew about the law from the start.

"It changes what we would order, but our nurses know the law and know it very well and can certainly advise someone as to what vaccine to take," said Genalee Alexander of the Columbia/Boone County Health Department.

No one knows just how many Missouri children may have gotten the flu vaccines containing thymersol, and leading health researchers say there's no proven harm from the compound.

State health officials say all providers should now stock the right flu vaccines for children and pregnant women.

Reported by Stephanie Cobb