Hartford, Conn. ? Just four doctors rolled up their sleeves for smallpox shots Friday in a feeble start for the U.S. government’s plan to vaccinate a half-million front-line health care workers across the nation in case of a bioterrorist attack.

Connecticut became the first state to take part in the vaccination program. The plan calls for 20 members of a “Genesis Team” to get the shots first and then fan out across the state to give the vaccine to other health professionals.

But the number of team members willing to get the shots dwindled amid reservations from hospitals, nursing unions and other professionals about the risk of deadly side effects from the vaccine.

By Friday, officials were expecting just nine volunteers, including a doctor to give the shots. The final turnout of four was a meager beginning to a plan touted as an important step toward protecting the public, but state officials said they expected to vaccinate the full team in the next two weeks.

State Health Commissioner Joxel Garcia said three nurses backed out after their union expressed reservations about the safety of the vaccine, one person withdrew for medical reasons and the fifth wanted more time to make the decision.

“I’m feeling fine, thank you,” Dr. Robert Fuller said after getting 15 rapid punctures from a two-pronged needle. The 38-year-old emergency room physician at the University of Connecticut Health Center added: “I know the risks.”

Dr. Walt Orenstein, head of the National Immunization Program at the federal Centers for Disease Control and Prevention, said modifications to the vaccine program would probably be needed. But there are no specifics yet.

“Until we begin the program and get some experience, it’s very difficult to know what needs to be done,” he said.

Dr. Robert Fuller, an emergency room physician at the University of Connecticut Health Center, is among the first smallpox vaccination recipients. He received his vaccination Friday at the University of Connecticut Medical Center in Farmington.

Routine vaccinations for smallpox in the United States stopped in 1972, but the idea was reintroduced in December by the government. Twenty states so far have requested the vaccine for members of their smallpox response teams.

Experts say as many as 40 people out of every million vaccinated for the first time will face life-threatening reactions and one or two will die.

The nurses’ union at the Health Center recommended waiting until compensation questions are resolved, saying it is unclear whether there is protection for people who get sick and miss work as a result of the vaccine, or for family members who might get sick through accidental exposure.

State lawmakers are working on legislation to clarify that workers’ compensation is available to program participants and that health insurance cannot be denied for adverse reactions.

The federal government has assumed some liability for the shots, but the protection applies only to negligence in manufacturing and administering the vaccine.