In the midst of an influenza epidemic and vaccine shortages, Delaware is temporarily changing its flu shot rules.

This week pediatrician and Director of Public Health Karyl Rattay temporarily lifted the ban on vaccines made with thimerosal, a preservative that contains trace amounts of mercury.

Normally, Delaware law forbids doctors from giving vaccine containing mercury to pregnant women and children younger than age 8.

Rattay said thimerosal has a proven safety record.

"Nonetheless, folks have had concern in the past that there might have been harm," she said.

Rattay said the Delaware ban on mercury-containing vaccines was enacted years ago, during a time of heightened, and never substantiated, concern over a connection between vaccines and autism.

In a statement, Rattay said pregnant women and young children are particularly vulnerable to the flu. "Public Health wants to ensure that vaccine is available for those who need it in Delaware," she said.

The division has been in touch with doctors and other health workers who are running low on mercury-free vaccine.

"They are not expressing concern about the risk from thimerosal. They are much more concerned about the risk of not being able to protect people from the risk of influenza," Rattay said.

Two people in Delaware have died from flu-related illness this month. At this time last year, there were no flu-related deaths reported in the state.

"We branded thimerosal with a scarlet letter," said Dr. Paul Offit, who heads the Division of Infectious Diseases at The Children's Hospital of Philadelphia. "And now there are people who are scared of thimerosal even though there is now abundant data showing that the level contained in vaccines was never harmful."

More than a decade ago, the Centers for Disease Control and Prevention began eliminating or reducing thimerosal in routine childhood vaccines. Delaware's law is unique in the region; neither New Jersey nor Pennsylvania has a similar rule.

"The notion that there still are states that have a preference against thimerosal-containing vaccines on their books is outdated, archaic and certainly not supported by the science," Offit said.

"Interesting that thimerosal has largely been taken out of childhood vaccines since the late '90s, and autism rates have gone up," Rattay said. "Which is the opposite of what would be expected if thimerosal was causing autism."