As Rhode Island prepares for the start of school-based swine-flu clinics Monday, one of the biggest unknowns is how many children will actually get the vaccine.

Some parents are fearful of the swine-flu vaccine –– or all vaccines. A recent Washington Post-ABC News poll found that nearly half of all parents in the United States said they would not vaccinate their children against swine flu. In New York City, fewer than half of parents have consented to flu shots for their children, with some schools seeing participation as low as 5 percent.

In Rhode Island schools, consent forms for the free and voluntary school clinics are coming in slowly, although it’s hard to know how many children will ultimately turn them in. Health Director David R. Gifford is expecting some last-minute decisions. “There’s still a lot of people asking questions –– is the vaccine safe or not?” he says. “They’re sort of trying to figure out what to do.”

Still, Gifford is predicting that 75 to 80 percent of school children will get the vaccine in the school-based clinics.

But why would even a fifth or a quarter of parents decline vaccination?

Parents are increasingly refusing all vaccines, fearing they are unsafe. Such fears spring from a lack of understanding combined with easy access to “abundant misinformation” on the Internet, says Dr. William Schaffner, chairman of the Department of Preventive Medicine at the Vanderbilt University School of Medicine.

A few years ago, Schaffner says, the National Foundation for Infectious Disease held focus groups with parents of young children in five cities. Consistently among all the groups, the people who were most adamant that their children must be vaccinated were parents who had emigrated from the developing world. These parents had vivid memories of the harm caused by vaccine-preventable illnesses.

“We have now been blessed with two solid generations of mothers and daughters who have been disease –free,” says Schaffner, who serves on the Network for Immunization Information steering committee. “They don’t know what measles is. They don’t know what German measles is, they don’t know polio, or diphtheria. And they’re not taught about these diseases.”

Meanwhile, the Internet teems with falsehoods about vaccines, including the disproven assertion that the preservative thimerosal causes autism.

Some people are comfortable with other vaccines, including the seasonal flu vaccine, but worry that the swine-flu vaccine was rushed into production and might not be safe.

“Sometimes when we try to communicate a good public health message, it may be perceived differently,” says Schaffner (who was Rhode Island’s state epidemiologist in the 1960s). “I have learned not to use the word ‘rush’. … I thought it was sending a positive message that vaccine makers are working very hard to get this to us as promptly as possible… What people hear is, ‘they must be cutting corners.’ ”

Dr. Nathan B. Beraha, a Lincoln pediatrician, often encounters such concerns. To alleviate them, he shows parents a chart depicting the prevalence of various strains of flu vaccine. He explains how the seasonal flu vaccine contains three strains of flu virus, while the swine-flu vaccine contains the H1N1. Otherwise, the vaccines are identical in their components and how they were made. In fact, H1N1 would have been included in the seasonal-flu vaccine had it been discovered in time. Beraha tells parents the swine-flu vaccine is safe.

When parents rebel against all vaccines, when they talk about government conspiracies and supposedly harmful ingredients, Beraha turns to anecdotes. He talks about two friends of his –– one needing crutches, the other in a wheelchair –– because of polio. He tells of a three-year-old killed by meningitis from bacteria now controlled by a vaccine. He talks about his own son, who got chickenpox before the vaccine was available –– and ended up in emergency surgery because of an infection in his ankle, a complication of chickenpox.

“There are things we used to see –– smallpox, chickenpox, measles, mumps –– that are gone because of vaccination,” Beraha says.

Big health-care companies like the Providence-based Lifespan hospital group have looked closely at vaccine refusal, because every year they try to persuade employees to get vaccinated against seasonal flu –– to protect patients, who are especially vulnerable.

As part of the campaign, officials ask employees who refuse to explain why. The answer has been consistently the same, says Donna Dube, director of Lifespan Employee Health Services: “They think they’re not going to get the flu. They’re strong and healthy.”

It’s an attitude similar, perhaps, to the person who doesn’t wear a seatbelt because he’s a good driver and believes he won’t get in an accident.

And the hospital has been counteracting it with information campaigns, including one-on-one peer discussions.

Another common misperception is that the flu shot can make you sick. The shot is administered at a time of year when many viruses are circulating. When someone comes down with a cold the day after getting the shot, they tend to blame the shot. But the illness most likely would have occurred anyway.

Nationally, the rate of flu vaccination among health-care workers hovers around 40 percent. Among all four hospitals in the Lifespan group, 71 percent took the seasonal flu vaccine this year, up 17 percent from previous years, Dube says. Additionally, Kent Hospital, in Warwick, and Memorial Hospital of Rhode Island, in Pawtucket, achieved similar seasonal-flu vaccination rates.

“Health care workers are asking for it,” says Dr. Philip Parks, medical director of Lifespan Health and Occupational Health Services. “They’re readily taking the vaccination.”

Lifespan expects a similar response when the swine-flu vaccine becomes available for health-care workers. “We have spoken to many employees,” Dube says. “I would say three to four weeks ago, there was reluctance. Now there’s tremendous interest. … They’re starting to feel comfortable that the vaccine is safe and they’re ready to go and get it.”

Dr. Marguerite Neill, a Brown medical professor and associate director of the Center for Biodefense and Emerging Pathogens at Memorial Hospital, fields many questions from patients and hospital employees about the flu vaccines, but sees little paranoia or deep distrust. Most people want to know how the H1N1 might affect them and when they can get their shot.

The attitude toward the flu has changed, Neill says.

“Five, six, seven years ago, there was really a complacency about influenza,” she says. “I think there just was a general lack of appreciation of the depths to which influenza can affect our patients as well as us.”

Now, especially with the recent death of a healthy 12-year-old girl from Bristol, people are taking the flu more seriously.

“We’re going to get through this,” Neill adds. “There have been pandemics in the past. …It may be rough. We’re in it together and we can survive it.”

ffreyer@projo.com