As more and more parents opt out of getting their children vaccinated, public health officials believe such decisions are causing a small spike in infection rates and even death rates of preventable illnesses.

Distrust of vaccinations lingers despite their having been administered to millions and millions of people over generations, saving untold lives.

Jennifer and Brian Cohen concede they are overly-involved parents, but say they became wary of any perceived risks -- including vaccinations -- when their twins survived a complex birth. 

"I was more afraid of the potential consequences from some of the vaccines and all of what is in the vaccine than I was of the original disease," Jennifer Cohen explained.

The Cohens are like so many other parents who remain skeptical of vaccinations despite mountains of scientific evidence.

In Miami-Dade County, immunization of kindergarteners has dropped from roughly 95 percent in 2006 to 79 percent last year. Rates in Broward are falling also, at rates just slightly behind.

The Center for Disease Control found that among distrustful parents, 27 percent felt too many shots are recommended, 26 were unsure vaccinations work, 25 percent believed it might cause autism, and 24 percent were concerned about possible side effects.

The Cohens delayed some vaccinations, and rejected others outright.

Meanwhile, infection rates are rising for everyone else, public health experts say, putting other kids at risk for measles, mumps, chicken pox, rubella, and the flu.

The distrust, they say, is fueled by misinformation like a recent claim from GOP hopeful Michelle Bachman that one vaccine caused "mental retardation." And much of the debate was fueled over the belief that autism was caused in part by vaccines.

Exhaustive government studies have concluded autism is not linked to vaccinations, but for folks like the Cohens the decision was made with only the best intentions.

"Going back to the mountains of evidence," Brian Cohen admits, "they've gone from inconclusive its conclusive. And they've reversed studies."

"This was something that I remember being up late at night in bed agonizing over," said his wife. "You know, we just want to do the right thing."