As Nicole Matten spoke about the sudden death of her 7-year-old daughter, she clasped a large, framed portrait of the smiling girl and held back her tears.
"She was perfectly healthy," Matten told a crowd outside Vermont's Department of Public Health in March. Kaylynne, she said, was healthy, until she was given a routine flu shot at her pediatrician's office last December. She fell ill almost instantly, she said, and was dead within days.
Matten was one of a handful of Vermont residents to rally against a bill that would make vaccines mandatory for school-aged children by eliminating "philosophical exemption" as a reason to opt out of the shots.
"Now, while we're grieving for our beautiful 7-year-old Kaylynne, we have to worry about our philosophical exemption being taken away for our other kids," said Matten. "It should be a parent's choice, this should be a free country."
Around the same time, inside the walls of the state Senate, Kayla Thomas, 19, of Rutland, Vt., emotionally described losing her 2-year-old brother to meningitis more than a decade ago. Now there is a vaccine available to prevent that illness.
"If the shot was around then he would still be here," Thomas said, in her testimony in support of vaccinations.
The debate over the bill has divided Vermont's families over the benefits and risks of vaccines. It has also pitted the state House-- whose majority voted down the bill -- against the state Senate, which voted to approve it.
Twenty states, including Vermont, currently allow philosophical exemptions for those who object to vaccines for personal or moral reasons.
"It's been clearly demonstrated that the broader (the) exemptions, the more loosely it's applied -- and the less likely children will get vaccinated," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University School of Medicine in Nashville, Tenn.
Fewer than 70 percent of children in Vermont between the ages of 18 months and 3 years received all of the recommended vaccines, according to a 2010 National Immunization Survey by the Centers for Disease Control and Prevention -- a rate lower than the 73 percent national average. Vermont has one of the highest philosophical exemption rates among those 20 states, Dr. Harry Chen, health commissioner for Vermont's Department of Public Health, told ABC News.
Measles and pertussis, also known as whooping cough, are the fastest growing vaccine-preventable diseases nationwide. Just last year, Vermont had an outbreak of pertussis. And other states with high philosophical exemption rates, including Washington and Oregon, have also seen a revival of pertussis.
According to the Vermont Coalition for Vaccine Choice, an advocacy group of parents, health care providers and others lobbying to stop the bill from passing, many people are naturally immune to communicable diseases without the need for vaccines.
The group also maintains that mass vaccinations will lower the risk of infection among people who decline the vaccinations, a phenomenon known as "herd immunity."