But thousands of children cared for by Homefirst Health Services in metropolitan Chicago have at least two things in common with thousands of Amish children in rural Lancaster: They have never been vaccinated. And they don’t have autism.

"We have a fairly large practice. We have about 30,000 or 35,000 children that we’ve taken care of over the years, and I don’t think we have a single case of autism in children delivered by us who never received vaccines," said Dr. Mayer Eisenstein, Homefirst’s medical director who founded the practice in 1973. Homefirst doctors have delivered more than 15,000 babies at home, and thousands of them have never been vaccinated.

The few autistic children Homefirst sees were vaccinated before their families became patients, Eisenstein said. "I can think of two or three autistic children who we’ve delivered their mother’s next baby, and we aren’t really totally taking care of that child -- they have special care needs. But they bring the younger children to us. I don’t have a single case that I can think of that wasn’t vaccinated."

The autism rate in Illinois public schools is 38 per 10,000, according to state Education Department data; the Centers for Disease Control and Prevention puts the national rate of autism spectrum disorders at 1 in 166 -- 60 per 10,000.

"We do have enough of a sample," Eisenstein said. "The numbers are too large to not see it. We would absolutely know. We’re all family doctors. If I have a child with autism come in, there’s no communication. It’s frightening. You can’t touch them. It’s not something that anyone would miss."

No one knows what causes autism, but federal health authorities say it isn’t childhood immunizations. Some parents and a small minority of doctors and scientists, however, assert vaccines are responsible.

This column has been looking for autism in never-vaccinated U.S. children in an effort to shed light on the issue. We went to Chicago to meet with Eisenstein at the suggestion of a reader, and we also visited Homefirst’s office in northwest suburban Rolling Meadows. Homefirst has four other offices in the Chicago area and a total of six doctors.

Eisenstein stresses his observations are not scientific. "The trouble is this is just anecdotal in a sense, because what if every autistic child goes somewhere else and (their family) never calls us or they moved out of state?"

In practice, that’s unlikely to account for the pronounced absence of autism, says Eisenstein, who also has a bachelor’s degree in statistics, a master’s degree in public health and a law degree.

Homefirst follows state immunization mandates, but Illinois allows religious exemptions if parents object based either on tenets of their faith or specific personal religious views. Homefirst does not exclude or discourage such families. Eisenstein, in fact, is author of the book "Don’t Vaccinate Before You Educate!" and is critical of the CDC’s vaccination policy in the 1990s, when several new immunizations were added to the schedule, including Hepatitis B as early as the day of birth. Several of the vaccines -- HepB included -- contained a mercury-based preservative that has since been phased out of most childhood vaccines in the United States.

Medical practices with Homefirst’s approach to immunizations are rare. "Because of that, we tend to attract families that have questions about that issue," said Dr. Paul Schattauer, who has been with Homefirst for 20 years and treats "at least" 100 children a week.

Schattauer seconded Eisenstein’s observations. "All I know is in my practice I don’t see autism. There is no striking 1-in-166," he said.

Earlier this year we reported the same phenomenon in the mostly unvaccinated Amish. CDC Director Dr. Julie Gerberding told us the Amish "have genetic connectivity that would make them different from populations that are in other sectors of the United States." Gerberding said, however, studies "could and should be done" in more representative unvaccinated groups -- if they could be found and their autism rate documented.

Chicago is America’s prototypical "City of Big Shoulders," to quote Carl Sandburg, and Homefirst’s mostly middle-class families seem fairly representative. A substantial number are conservative Christians who home-school their children. They are mostly white, but the Homefirst practice also includes black and Hispanic families and non-home-schooling Jews, Catholics and Muslims.

They tend to be better educated, follow healthier diets and breast-feed their children much longer than the norm -- half of Homefirst’s mothers are still breast-feeding at two years. Also, because Homefirst relies less on prescription drugs including antibiotics as a first line of treatment, these children have less exposure to other medicines, not just vaccines.

Schattauer, interviewed at the Rolling Meadows office, said his caseload is too limited to draw conclusions about a possible link between vaccines and autism. "With these numbers you’d have a hard time proving or disproving anything," he said. "You can only get a feeling about it.

"In no way would I be an advocate to stand up and say we need to look at vaccines, because I don’t have the science to say that," Schattauer said. "But I don’t think the science is there to say that it’s not."

Schattauer said Homefirst’s patients also have significantly less childhood asthma and juvenile diabetes compared to national rates. An office manager who has been with Homefirst for 17 years said she is aware of only one case of severe asthma in an unvaccinated child.

"Sometimes you feel frustrated because you feel like you’ve got a pretty big secret," Schattauer said. He argues for more research on all those disorders, independent of political or business pressures.

The asthma rate among Homefirst patients is so low it was noticed by the Blue Cross group with which Homefirst is affiliated, according to Eisenstein.

"In the alternative-medicine network which Homefirst is part of, there are virtually no cases of childhood asthma, in contrast to the overall Blue Cross rate of childhood asthma which is approximately 10 percent," he said. "At first I thought it was because they (Homefirst’s children) were breast-fed, but even among the breast-fed we’ve had asthma. We have virtually no asthma if you’re breast-fed and not vaccinated."

Because the diagnosis of asthma is based on emergency-room visits and hospital admissions, Eisenstein said, Homefirst’s low rate is hard to dispute. "It’s quantifiable -- the definition is not reliant on the doctor’s perception of asthma."

Several studies have found a risk of asthma from vaccination; others have not. Studies that include never-vaccinated children generally find little or no asthma in that group.

Earlier this year Florida pediatrician Dr. Jeff Bradstreet said there is virtually no autism in home-schooling families who decline to vaccinate for religious reasons -- lending credence to Eisenstein’s observations.

"It’s largely non-existent," said Bradstreet, who treats children with autism from around the country. "It’s an extremely rare event."

Bradstreet has a son whose autism he attributes to a vaccine reaction at 15 months. His daughter has been home-schooled, he describes himself as a "Christian family physician," and he knows many of the leaders in the home-school movement.

"There was this whole subculture of folks who went into home-schooling so they would never have to vaccinate their kids," he said. "There’s this whole cadre who were never vaccinated for religious reasons."

In that subset, he said, "unless they were massively exposed to mercury through lots of amalgams (mercury dental fillings in the mother) and/or big-time fish eating, I’ve not had a single case."

Federal health authorities and mainstream medical groups emphatically dismiss any link between autism and vaccines, including the mercury-based preservative thimerosal. Last year a panel of the Institute of Medicine, part of the National Academies, said there is no evidence of such a link, and funding should henceforth go to "promising" research.

Thimerosal, which is 49.6 percent ethyl mercury by weight, was phased out of most U.S. childhood immunizations beginning in 1999, but the CDC recommends flu shots for pregnant women and last year began recommending them for children 6 to 23 months old. Most of those shots contain thimerosal.

Thimerosal-preserved vaccines are currently being injected into millions of children in developing countries around the world. "My mandate ... is to make sure at the end of the day that 100,000,000 are immunized ... this year, next year and for many years to come ... and that will have to be with thimerosal-containing vaccines," said John Clements of the World Health Organization at a June 2000 meeting called by the CDC.

That meeting was held to review data that thimerosal might be linked with autism and other neurological problems. But in 2004 the Institute of Medicine panel said evidence against a link is so strong that health authorities, "whether in the United States or other countries, should not include autism as a potential risk" when formulating immunization policies.

But where is the simple, straightforward study of autism in never-vaccinated U.S. children? Based on our admittedly anecdotal and limited reporting among the Amish, the home-schooled and now Chicago’s Homefirst, that may prove to be a significant omission.