Michael Meehan and Thomas Dysarz are so concerned about the risk of a brain disorder from vaccinations for their quadruplets that they are refusing recommended immunizations and have been told to look for a new doctor.

Monica Wainscott, a mother of quintup-lets, can't imagine not immunizing her babies, whose lives seemed so fragile at birth.

The families represent the two sides of a national debate about the safety of vaccines.

Some parents, politicians, and researchers say that the minuscule amounts of mercury in vaccines could be responsible for a range of disorders, including autism.

The issue, raised during the 1990s, has received renewed attention recently from parents and advocates who met earlier this month on Capitol Hill. They asked the nation's leaders and pharmaceutical companies to stop the use of the mercury-containing preservative thimerosal in all vaccines, contending that illness and disability are resulting.

But other researchers and physicians say that the risks are small and that not getting the immunizations could be deadly.

"There is only a minuscule risk. The benefits far outweigh the risks," said Craig Gillispie, an administrator for Pediatric and Adolescent Associates, which dropped the quadruplets as patients because Meehan refused vaccinations.

Meehan is the quadruplets' biological father and Dysarz, his male partner, is helping to raise them since they were born two months prematurely in July.

Wainscott, the Frankfort mother of 13-month-old quintuplets, said she was not aware of the concerns about thimerosal, but thinks it is imperative to get the vaccines.

"The risks are outweighed by what could happen to them if they don't receive the immunizations. They were so sick in the neonatal intensive-care unit. We don't want to go down that road again," she said.

In 2001, the Institute of Medicine recommended that children and pregnant women avoid thimerosal.

According to The National Center for Disease Control, all seven vaccines produced since April 2001 and recommended for use among all children do not have thimerosal or have only trace amounts.

Even as vaccines containing thimerosal are being phased out, CDC officials say they are still safe.

But it's the trace amounts that concern parents. Like lead exposure, there is no "safe" level for mercury, said Sallie Bernard, Director of the group Safe Minds.

The principal ingredient of thimerosal is ethylmercury, a chemical cousin of the methylmercury found in mercury-contaminated fish. For years, ethylmercury was used in multidose vials of vaccines to prevent contamination by bacteria when a syringe needle was injected into the vial repeatedly.

Boyd Haley, chairman of the University of Kentucky Chemistry Department, has testified on Capitol Hill and his concerns about thimer-osal have been published in medical journals.

"Thimerosal is a severely neurotoxic compound," Haley said. "If it was my child or my grandchild, I would not give them the vaccinations. It's not worth the risk."

Meehan said he is not ruling out every immunization, just those that contain thimerosal. Meehan and Dysarz are most concerned about the shots for diphtheria, tetanus and pertussis and hepatitis B.

They agreed, however, to have the babies immunized against RSV, a lung ailment. That vaccine does not contain thimerosal.

Meehan and Dysarz gained international attention when a Nicholas-ville woman gave birth to Meehan's biological quadruplets through in-vitro fertilization, a situation that has drawn extremes of criticism and support.

The men say the immunization issue and their disagreement with their doctors has nothing to do with the fact that they are the gay parents of quadruplets.

"This is an issue for everyone," Dysarz said.

Gillispie declined to discuss the quadruplets' case specifically, but said: "If patients do not follow the physician's prescribed treatment protocol, we don't keep them as patients."

Lexington pediatrician Thomas Pauly, who cares for the Wainscott quintuplets, said he wouldn't treat the quadruplets if Meehan and Dysarz didn't agree to recommended immunizations. "My job is to prevent disease and I would not be doing my job. It's a mistake not to immunize," he said.

A study released in November by researchers from the University of Rochester Medical Center bolstered the argument that the vaccines are safe.

But Haley and others worried about thimerosal point to another study released in October by researchers at University of California-Davis, which concluded that the nearly threefold surge in California's autism rate, which now stands at 4 to 5 per 10,000 people, could not be explained by shifting definitions, misclassification or migration.

Maquel Sarantakos, 32, a school librarian from Jessamine County, had some reservations, but her decision to get vaccinations for her daughter, Genaea, 4, was guided by experience and advice from her pediatrician.

A key event was when a pregnant colleague feared she had been exposed to rubella, also known as German measles. Such exposure can cause serious birth defects, including blindness and heart abnormalities. It influenced Sarantakos to make sure her own immunizations were up to date before she got pregnant.

She realized the risk, though rare, was real.

"Measles still do happen," she said. "I don't want to take the chance. I wouldn't want my daughter to have that exposure."

"We would worry with each shot," said Michelle Hintz, 33, a Lexington mother of three. "But we felt we had to do it." She and her husband debated the benefits and drawbacks of vaccines for their first two children, now 6 and 3, and decided to have them immunized.

Their third child, now 1, was born at home. A growing interest in alternative health increased their doubts about immunizations, so they've delayed many of his shots.

"It's getting by on everyone else taking a risk," she said. "But there's no easy answer. We're kind of in limbo about what to do."

The concept is known as "herd immunity." Even those who are not immunized are somewhat protected because the vast majority of the population is not able to spread a disease. But as the unvaccinated population grows, so does the risk.

Ultimately, Hintz expects to get her youngest immunized. "We're going to be pushed, because of the risks, and because those diseases are out there. We're probably going to pick and choose which ones."

Kentucky children must be immunized before attending school, but Debbie Rickerd, a registered nurse and team leader of the immunization clinic at the Lexington-Fayette County Health Department, said parents who don't immunize for medical or religious reasons can sign a waiver.

"The chances of having a reaction is slim, much smaller than coming into contact with a disease that could be deadly," Rickerd said.

Meanwhile, Meehan and Dysarz say they will look for a pediatrician. Until then, the quadruplets can receive emergency medical care at area hospitals. Meehan is confident he can find a Lexington pediatrician who will work with them, because other parents with similar concerns across the country have been successful.

Gillispie, the administrator at Pediatric and Adolescent Associates, said it's not unusual for parents whose children are treated at their practice to be concerned about the immunizations.

"But it is unusual for them to be extremely adamant," Gillispie said.

The national debate over vaccinating children is playing out in Bluegrass doctors' offices, too