For Maryland resident Victoria Katona, choosing to vaccinate her children was a no-brainer. The issue also helped her picked her pediatrician, who first broached the topic while she was pregnant with her first child. During a prenatal interview, the doctor asked whether Katona planned to vaccinate her child because his office had a strict policy against treating unvaccinated children and those who delay vaccinations.

“That’s important to me because I didn’t want my newborn child in an office with someone who may have whooping cough or be shedding measles,” said Katona, who now has two children ages 4 and 5. “Why wouldn’t you get them vaccinated? It’s what you do -- to make sure your children are safe and not going to be sick.”

In the wake of the worst measles outbreak the U.S. has seen in decades, some doctors are turning away unvaccinated children to protect individuals, such as cancer patients and young babies, who cannot receive live vaccines and depend on the health of others. It’s a choice that every parent must make, and one that has launched a national conversation that could have dire social, medical and even legal consequences for parents and children alike.

Katona, who lives just outside Baltimore, said she would switch physicians if the office changed its policy on treating unvaccinated children, although she’s confident this will not happen. “If [my pediatrician] were willing to look past something that important, what’s to say that she wouldn’t circumvent other important medical issues,” she said. “Could I trust that she would be providing appropriate medical care to my children?”

Most parents in her community immunize their children, and those who don’t aren’t showing up at her pediatrician’s office, Katona said. “I imagine those doctors that don’t require vaccinations are well-known among the anti-vaxing groups. From my experience, nonvaxing parents ask around to see who they can go to without being pressured into vaccinating,” she said.

In contrast, Karen Ernst takes her fully vaccinated children to a physician who strongly encourages immunization, but will still see patients who are skipping or delaying shots. “The risk to my children is very low because they’ve received all vaccinations. I’m not necessarily worried about measles coming through the door,” said Ernst, a mother of three in St. Paul, Minnesota.

Ernst said she might have felt otherwise had there been a measles outbreak when she was choosing a pediatrician. “If I was doing it all over again and I was to have a new baby, I might be a little bit afraid to bring my child to an office that did see unvaccinated children,” said Ernst, who helped relaunch Voices for Vaccines in 2013. It’s a parent-led organization that advocates for on-time vaccination and the reduction of vaccine-preventable disease.

Pushback From Pediatricians

Experts said there’s been a growing number of people in the last decade that have decided against immunization. As a result, some pediatricians across the country have become frustrated with parents who are opting out of childhood vaccinations.

“There are a lot of pediatricians who are worried about this,” said Arthur L. Caplan, who heads the division of medical ethics at New York University Langone Medical Center. “Most pediatricians will still work with you even if you don’t vaccinate. But the percent that won’t is growing, and the measles outbreak is accelerating it.”

The pediatricians who are now refusing unvaccinated patients are doing so out of mounting frustration, because measles is a vaccine-preventable disease, Caplan noted.

The ongoing measles outbreak is linked to Disney theme parks in California and has spread to 102 cases across 14 states since December. It’s the largest number of cases the U.S. has seen since measles was declared eliminated in 2000, according to the U.S. Centers for Disease Control and Prevention.

Dr. Mark Sawyer, an infectious-disease committee member at the American Academy of Pediatrics, said the vast majority of these cases are unvaccinated individuals. “The general community of pediatricians is getting a little tired of these outbreaks linked to people intentionally not vaccinating their kids,” he said. “Clearly, this outbreak has smoldered along longer than others do, and that may drive some to say, ‘You know what, I’ve had enough of this, I’m worried about my waiting room.’”

Sawyer said pediatricians will refuse unvaccinated patients for a number of reasons, including the risk they pose to other individuals in the waiting room, such as young children who are not yet eligible for immunization. Physicians will also turn away parents who are opposed to vaccinating because it suggests a lack of confidence in the doctor’s overall care. “Pediatricians feel very strongly that vaccination is a very important preventative step that provides care,” Sawyer said. “They feel that parents who don’t follow their recommendation are not letting them take good care of their patients, and that’s a very difficult position for pediatricians to believe in.”

But vaccines are not perfect, he said. One dose of the measles, mumps and rubella, or MMR, vaccine is 95 percent effective against the measles virus, while two doses are 99 percent effective. In other words, one in 20 single-dose vaccinated individuals are still susceptible to contracting measles during an outbreak, according to Sawyer, who is also a professor of pediatrics at the University of California San Diego School of Medicine and Rady Children’s Hospital.

There are also some adverse but extremely rare side effects from the MMR vaccine. One in six people has a fever within a week of getting a measles shot, about 5 percent of people experience a mild rash, and about 1 percent notice some swelling in their glands. Meanwhile, a severe allergy to the vaccine appears less than once in a million administered doses, according to the CDC.

Brain damage and coma suffered after the shot is so uncommon that it’s difficult to decipher whether immunization is the cause, while vaccines are usually administered around the same time a child is flagged for autism, according to ABC News. Scientific studies have also long disproved any link between autism and the MMR vaccine, experts have said.

According to the CDC, 69 people who received shots have died since 2004, but their deaths were not necessarily direct results of the vaccine because the agency’s protocol for reporting adverse reactions merely correlates them, Newsweek reported.

Parents Against Vaccines

In 2014, all 50 states allowed a medical vaccine exemption; 48 states and the District of Columbia allowed a religious vaccine exemption; and 17 states allowed a philosophical, conscientious or personal belief exemption. Moreover, the exemptions are worded differently in each state. Families citing medical exemptions constitute a small number of those who don’t vaccinate. In California, there were about 1,000 medical exemptions and more than 17,000 philosophical exemptions from immunization in the 2013-2014 school year, CNN reported.

Dr. Sydney Z. Spiesel, a clinical professor of pediatrics at the Yale School of Medicine, said the varying state laws on vaccine exemptions can make it difficult for pediatricians to enforce immunization. The number of licensed doctors who are against vaccinating is very small, but the business can be lucrative, he said. “The pediatricians [against vaccines] are doing it because it attracts attention or money,” said Spiesel, who runs a private practice in Woodbridge, Connecticut. “I think the great majority of pediatricians everywhere are strong believers in immunization.”

Spiesel said the anti-vaccine movement in the U.S. has dramatically waned, due to pushback from pediatricians amid the ongoing measles outbreak. Parents who were once vaccine-hesitant are now lining up to have their children immunized. “Now, suddenly, they’re beginning to understand there really is a risk. There really is measles out there, and measles is a potentially lethal disease,” he said.

The Anti-Vaccine Movement

Some parents who are hesitant about vaccines have been drawn into an anti-vaccine movement that often cites debunked research. In 1998, a prominent British medical journal published research by Andrew Wakefield, who suggested the combined MMR vaccine could cause autism. However, this article was retracted by the publication in 2010, after years of reassessment determined Wakefield had been dishonest and misleading, while violating basic rules of research ethics, according to the New York Times. Wakefield was subsequently stripped of his medical license in the U.K., CNN reported at the time.

Anti-vaccine groups have also expressed concern over thimerosal, a vaccine preservative containing mercury. However, thimerosal was removed from the final product of nearly all vaccines -- including the MMR vaccine -- in the U.S. by 2002, due to mounting public pressure rather than sound science, as a wealth of scientific studies have shown thimerosal-containing vaccines do not cause neurodevelopment disorders, according to experts.

The MMR vaccine, developed by John Enders in the late 1950s and universally distributed by the late 1960s, is most effective against the measles virus when delivered in two doses. However, some vaccine-hesitant parents believe spacing out immunization shots is best for their children’s health.

Dr. James Cherry, a professor of pediatrics at the David Geffen School of Medicine at University of California, Los Angeles, recommended against this. “The idea that multiple vaccines together overload the immune system, or to start them later and space them out -- that whole idea is just ridiculous,” he said.

Cherry, who is also an attending physician at the Mattel Children’s Hospital UCLA, said five decades of vaccinations are responsible for the consistently low number of measles-related deaths in the U.S. Tremendous public-health efforts to encourage immunization and quarantine infected individuals have curbed the current outbreak, he added. “If we were to not have a vaccine today, we’d have about 3,000 deaths per year,” Cherry said. “Vaccines save a lot of lives.”