Ever since a British doctor published a study in 1998 suggesting that some vaccines may contribute to autism, the number of parents refusing vaccines for their children, or demanding an “alternative’’ immunization schedule, has steadily grown.

And even though that paper has since been discredited, and scores of peer-reviewed studies have failed to find any link between vaccines and autism, the suspicion that vaccines are dangerous has stuck.

“I never really liked how many vaccinations a baby was getting,” said Anna Popp, an Easthampton librarian who allowed her 5-year-old daughter to get some of the recommended vaccines, but not all, and delayed other vaccinations beyond the age that doctors say is safe. “I just felt, if I could put some of those off until later, I would rather not overburden my child’s system with a bunch of toxic organisms.”

Popp knows that following her own rules on immunization puts her — and many other vaccine skeptics — at odds with the medical establishment. Popp lives in Western Massachusetts, where the percentage of parents choosing not to vaccinate their children is well above the state average….