AUGUSTA — Three or four families per 100 in Maine opt out of mandatory vaccinations for school-aged children, and state officials are concerned.

In Maine, the rate of vaccination exemptions was 3.56 percent during the 2009-10 school year, according to the latest data from the Maine Center for Disease Control and Prevention. That’s slightly below the national average of five families per 100.

Peter Smith, director of the division of infectious disease for the agency, said the exemption rate has fluctuated in Maine over the last several years. The highest exemption rate was 4 percent in 2007-08. Data on individual counties is unavailable.

Smith said the vaccination policy, which requires children to be vaccinated before entering elementary school, was generated by United States Department of Health and Human Services and used nationwide.

The vaccines required in all states are for diphtheria, tetanus and pertussis (DTAP); measles, mumps and rubella (MMR); and polio. Maine requires an additional vaccine for chicken pox, also known as varicella.

Compliance data comes from individual school districts, Smith said.

“The schools are responsible for checking the immunization history and recording any exemptions,” he said.

There are three categories parents can cite for exemption: medical, philosophical and religious reasons, he said.

“Medical tends to be less than half a percent, and the remainder fall into the broader categories of religious and philosophical exemptions,” he said.

Smith said some parents may choose to opt out because of misinformation on the Internet, and it’s difficult to combat those perceptions.

“I think the parents who opt out of immunization are doing something — in their view — to protect their children,” he said. “They’re doing it in a way that is against better advice from, say, infectious disease societies and pediatric associations and state health agencies and federal health agencies, but they’re still doing it with the interest of protecting their children.”

Financial constraints may also play a role, he said.

“We do know there are financial barriers to vaccination. Even with insurance, the out-of-pocket costs can be pretty high,” Smith said.

Assistance is on the way for Maine families who opt out for financial reasons, said Peter Gore, chairman of the Maine Vaccine Board. As of Jan. 1, the out-of-pocket costs for vaccinations will effectively be zero.

Legislation signed in 2010 allows the Maine Vaccine Board to distribute no-cost vaccines to health providers throughout the state beginning next year. Gore said there may be costs associated with administering the shots, but the vaccines themselves will be free to patients. There is no cost to Maine taxpayers, he said.

Smith said there the consequences of opting out are real.

“One thing we know is these diseases are still out there,” he said. “When immunization rates go down, we see more cases and we see more outbreaks. That happens nationwide.”

Ben McCanna — 861-9239

bmccanna@centralmaine.com