Boston Sabrina Rahim doesn't practice any particular faith, but she had no problem signing a letter declaring that because of her deeply held religious beliefs, her 4-year-old son should be exempt from the vaccinations required to enter preschool.
She is among a small but growing number of parents around the country who are claiming religious exemptions to avoid vaccinating their children when the real reason may be skepticism of the shots or concern they can cause other illnesses.
An Associated Press examination of states' vaccination records and data from the Centers for Disease Control and Prevention found that many states are seeing increases in the rate of religious exemptions claimed for kindergartners.
"Do I think that religious exemptions have become the default? Absolutely," said Dr. Paul Offit, head of infectious diseases at Children's Hospital in Philadelphia and one of the harshest critics of the anti-vaccine movement. He said the resistance to vaccines is "an irrational, fear-based decision."
The number of exemptions is extremely small in percentage terms and represents just a few thousand of the 3.7 million children entering kindergarten in 2005, the most recent figure available.
But public health officials say that it takes only a few people to cause an outbreak that can put large numbers of lives at risk.
"When you choose not to get a vaccine, you're not just making a choice for yourself, you're making a choice for the person sitting next to you," said Dr. Lance Rodewald, director of the CDC's Immunization Services Division.
State standards vary
All states have some requirement that youngsters be immunized against such childhood diseases as measles, mumps, chickenpox, diphtheria and whooping cough.
Twenty-eight states, including Florida, Massachusetts and New York, allow parents to opt out for medical or religious reasons only. Twenty other states, among them California, Pennsylvania, Texas and Ohio, also allow parents to cite personal or philosophical reasons. Mississippi and West Virginia allow exemptions for medical reasons only.
From 2003 to 2007, religious exemptions for kindergartners increased, in some cases doubled or tripled, in 20 of the 28 states that allow only medical or religious exemptions, the AP found. Religious exemptions decreased in three of these states - Nebraska, Wyoming, South Carolina - and were unchanged in five others.
While some parents - Christian Scientists and certain fundamentalists, for example - have genuine religious objections to medicine, it is clear that others are simply distrustful of shots.
Some parents say they are not convinced vaccinations help. Others fear the vaccinations themselves may make their children sick and even cause autism.
Even though government-funded studies have found no link between vaccines and autism, loosely organized groups of parents and even popular cultural figures such as radio host Don Imus have voiced concerns. Most of the furor on Internet message boards and Web sites has been about a mercury-based preservative once used in vaccines that some believe contributes to neurological disorders.
Unvaccinated children can spread diseases to others who have not gotten their shots or those for whom vaccinations provided less-than-complete protection.
In 1991, a religious group in Philadelphia that chose not to immunize its children touched off an outbreak of measles that claimed at least eight lives and sickened more than 700 people, mostly children.
And in 2005, an Indiana girl who had not been immunized picked up the measles virus at an orphanage in Romania and unknowingly brought it back to a church group. Within a month, the number of people infected had grown to 31 in what health officials said was the nation's worst outbreak of the disease in a decade.