BOSTON – The state Department of Public Health on Wednesday issued an order limiting distribution of the scarce influenza vaccine to people considered “high risk” for the virus.

Public Health Commissioner Christine Ferguson said the state, facing an unparalleled shortage of flu shots, had to direct vaccinations to people most likely to die from the illness, such as very young children, seniors over 65 and people with chronic medical conditions.

“It’s not rationing,” she said. “It’s being rational about how to reduce the number of deaths that could result from a serious flu season.”

The order also requires health care providers to report flu shot supplies to the state. Ferguson said the state had no plans to take over private supplies, though she said, “It’s not impossible.” Rather, she said, the state can better lobby for its share of the 22.4 million doses the federal government plans to distribute if it has a handle on its own supplies.

Health care providers who defy Ferguson’s order face a maximum penalty of a $200 fine per infraction and six months in jail.

A state order controlling what the private sector can do with its own medicine is “unprecedented,” and makes it difficult for public flu shot clinics to continue, since many can’t verify a “high risk” status for patients, said Dr. John Foster, medical director of the North End Rehabilitation and Nursing Center, a nursing home. But he added the order is needed.

“I think it is a public health crisis,” he said. “They can’t wait and give vaccines out to people who shouldn’t get it.”

About 60 percent of the state’s flu vaccine is generally distributed by doctors, health clinics and other private parties, Ferguson said. The rest is given out by the state.

Last week, British regulators unexpectedly shut down a major U.S. vaccine supplier, Chiron Corp., citing concerns about bacterial contamination. The move froze shipment of up to 48 million flu shots.

The state had ordered about 610,000 shots, including about 450,000 from Chiron and 160,000 from another supplier, Aventis Pasteur, Ferguson said. The state has received about 80,000 doses from Aventis, she said. DPH should know within days how many of the 22.4 million undistributed doses it will receive.

About 800 to 1,000 people die of influenza annually in Massachusetts, according to state health officials. The state has about 2 million people who would be considered “high risk,” but only about 40 percent are immunized annually.

The state’s prime flu season is December to March, with most vaccinations given out in late October and early November. Ferguson said it’s too early to panic about a shortage, but not too early to ensure vaccinations get to the people who need it most.

“I think we’re in a tough spot, but not an impossible one,” she said

The “high risk” group includes the following:

– Children ages 6 months to 23 months.

– Adults age 65 and over.

– Anyone six months and older with chronic medical conditions, such as heart disease, asthma and diabetes.

– Out of home caregivers and household contacts of children younger than six months.

– Residents of nursing homes and long term care facilities.

– Children six months to 18 years on chronic aspirin therapy.

– Health care workers who have direct contact with patients.