LAND O'LAKES — Melanie Dymond kept talking to her pediatrician for months, looking for reassurance.
In the end, she just couldn't give her son Dayton the MMR shot.
"I couldn't fathom him getting the shot, because I know that's the one that's linked to controversy," she said.
Instead, she drove her baby, now 2, across town to get the measles, mumps and rubella vaccines one at a time, instead of as a 3-in-1 shot.
Each one cost Dymond, 39, more than $80, but she says it's worth it.
Separating or delaying vaccines has become a fallback for parents who worry but don't want to take the drastic step of refusing to vaccinate. Pediatrician Bob Sears, son of the well-known authors of The Baby Book, has made his own mark by developing an "alternate" schedule, spacing some vaccines out for weeks, others for years.
"I think there's not been enough safety research to really prove that the high number of vaccines we're giving is definitely safe," Sears said. "As a doctor, I felt that it was prudent that until we prove that giving so many shots together is safe, I've spread my shots out."
Sears admits his schedule has a downside: more office visits. For a young baby, he advises monthly visits with two shots each time, rather than the CDC schedule, which calls for fewer visits, but more shots. The 2-month visit, for example, calls for five or six shots.
While many parents find Sears' schedule a reassuring option, leading vaccine scientists say it isn't necessary — and some point out that delaying shots carries other risks. Tampa pediatrician Marcy Baker said she's willing to space shots out for a few weeks for reluctant parents — but not months or years.
"Everything's a plane ride away," Baker said. "A global society means global germs, too."
Parents shouldn't worry that multiple vaccines are "overloading" the immune system, said Dr. John Iskander, acting director of immunization safety at the federal Centers for Disease Control and Prevention.
"We have pretty good evidence that's not the case," Iskander said. "The number of antigens you are exposed to in vaccines is pretty small, compared to what you're exposed to in everyday life."
Although babies got fewer vaccines years ago, the old vaccines had more antigens, or foreign substances for which people produce antibodies, than today's vaccines, Iskander said. The old pertussis shot had about 3,000 antigens. The new version has two to five.
Sears agrees "that's probably true," and says he has seen no evidence of harm from vaccines. Still, he is concerned about chemicals in vaccines, such as aluminum and formaldehyde.
"We know that aluminum that's swallowed is very safe," he said. "But aluminum that's injected has to be processed by your body and then eliminated."
Vaccine scientists disagree. They point out that babies get far more aluminum from breast milk and formula than the trace amount found in vaccine.
Despite such reassurances, separating vaccines has clearly struck a nerve. Passport Health of Tampa Bay, where Dymond got Dayton's shots, has seen a steady increase in parents wanting separate shots since the business first offered them two years ago.
Most pediatricians don't stock separate shots, said nurse Duellyn Pandis, Passport's executive director in Tampa.
Pandis isn't sure whether there's any link between vaccines and autism. But she thinks offering the shots separately is better than going without.
"Rather than not vaccinating the child at all, it's something we looked into and thought was worthwhile," Pandis said.