She and her husband, Michael Beglinger, 51, live with their three children in Los Angeles, where a measles outbreak has pushed some parents to extremes in a heated debate over vaccination.

The area is one of a few pockets across the United States where a small but significant number of parents delay vaccinations until they believe their children's immune systems are strong, or refuse them altogether, citing much-disputed reports that vaccines can cripple children. Other parents, and much of the medical establishment, accuse them of endangering the larger population.

The U.S. Centers for Disease Control and Prevention (CDC) and medical experts say that at least 92 percent of children should be vaccinated to create enough of a herd-immunity effect to protect a community. So even a fairly small number of unvaccinated children can be a big issue in places like California, wherestatewide vaccination rates with the MMR (measles, mumps, and rubella) shot hover right around 92 percent.

To Aquino, the debate over vaccinations isn't political, or even religious, as it is for many others who view immunizations warily. Nearly 20 years ago, her daughter, Sophie Beglinger, now 19, received her first round of the diphtheria, pertussis, and tetanus (DPT) vaccine. Days later, Sophie developed spasms. The doctor withheld the second round of the pertussis vaccine because in rare cases, febrile seizures can be one of the side effects.

According to the CDC, the DTaP vaccine (the updated version of the DPT shot Sophie got) can cause mild to moderate side effects, including fever in one in four cases and mild seizures in 1 in 14,000. The agency describes long-term seizures and permanent brain damage as being "so rare it is hard to tell if they are caused by the vaccine."

For nearly 20 years, Sophie has had multiple grand mal seizures and hundreds of smaller seizures every day. She is unable to express herself or care for her own bodily needs. She convulses so routinely during dinner that when her brothers sense a seizure coming on, one automatically gets a pillow while the other lays her down on the floor.

"I don't even know if the vaccine caused her seizures," Aquino said. But the onset of Sophie's seizures "was suspiciously close. The doctor said it might be [related]."

View Images Michael Beglinger ties Sophie's shoes as he prepares her to go outside for a walk. The walls of her bedroom are covered with purple padding to protect her when she falls or butts her head against them. Photograph by Emily Berl, National Geographic

For Aquino and her family, the doubts and fears linger to this day. "No doctor of Sophie's has said, absolutely not, it wasn't the vaccine."

Playing the Odds

Right now, the debate over vaccinations is focused on one disease: highly contagious measles. The current national outbreak is believed to have started at the Disneyland amusement park in Anaheim, California, spread by an infected visitor who was at the park in December.

Alan R. Hinman, director of the Center for Vaccine Equity at the Task Force for Global Health, in Decatur, Georgia, says the likelihood of a debilitating reaction to the measles vaccine is "near vanishing." Before the measles vaccine was introduced in 1963, he adds, measles killed 400 to 500 people a year in the United States. The disease was considered eliminated by 2000.

Some doctors recommend single-dose vaccines and delaying vaccinations until a child's immune system is stronger, and that is the approach that Aquino and Beglinger use, along with some parents like them.

But Hinman says that delaying vaccines leaves a child vulnerable to disease for a longer period of time and makes that child a risk to other children too young to get the vaccine, as well as to people who can't be inoculated because they have immune deficiencies.

View Images The whole family helps care for Sophie amid active lives outside the home. The family dog, Valentine, watches as Henry Beglinger leaves for lacrosse tryouts. Oliver Beglinger adjusts his bicycle helmet. Photograph by Emily Berl, National Geographic

"This is not just a individual decision," Hinman said. "It's a decision that affects the whole community."

A Generational Decision

Sophie's 13-year-old brother, Oliver—like any teenager—wants to be like his friends. And his friends are vaccinated against measles (most children receive two doses of the MMR vaccine before age six). But when Aquino told her son it was time for him to do the same, he balked.

"He's conflicted," Aquino said. "He sees what his sister is like, and it's not that far a stretch for him to imagine, 'What if that happened to me?'"

Aquino has encouraged him to go through with the vaccinations because his immune system is strong, but they've decided to wait until Oliver feels ready.

Aquino sounds conflicted too. She's certain she is doing the right thing by her children. But when asked how she would respond to parents who might say her unvaccinated children are endangering their children, she swings between angst and reproach.

"I know that there is a small chance that you could get something even if you're vaccinated ... I'd be horror-stricken," she said of the prospect that her child could spread preventable disease. "I'd be so upset. But it wouldn't be intentional. I don't think the risk is that great, frankly."

She said she's not worried, in part, because she comes from a generation in which she and most of her friends all got measles without serious complications. According to a recent Pew Research Center study, about 9 percent of the population isn't fully convinced about the safety of vaccines.

Some poll respondents expressed skepticism about the effectiveness of vaccines, while others question why healthy children should be given the vaccines. Others say they distrust pharmaceutical companies. (See "Young Adults Most Worried About Vaccines, Poll Finds.")

View Images A hallway photo gallery in the Beglinger home captures the benchmarks of their kids growing up, including Sophie's moments of joy and tranquility. Photograph by Emily Berl, National Geographic

Aquino is part of an even smaller subset of this 9 percent: those who aren't "anti-vaccine" but worry about potential health effects enough to delay or skip some vaccinations.

Rare Cases

At the time Sophie developed seizures, her mother couldn't just check the Internet for information.

Instead, Aquino went to a bookstore, where she found a single book with a two-line mention of infantile spasm. She learned there was a 92 percent chance that Sophie would not only be epileptic, but mentally retarded as well.

Aquino and Beglinger have not been able to prove a causal link between their daughter's condition and the vaccine. If they could, they might be eligible for compensation from the National Vaccine Injury Compensation Program, or NVICP, which is funded by pharmaceutical companies.

NVICP was formed in 1988 to create a federal no-fault, non-adversarial alternative to suing vaccine manufacturers and providers in civil court. The program is funded by a 75-cent tax collected by pharmaceutical companies on every vaccine.

A 2014 report by the U.S. Government Accountability Office faulted the NVICP for not making its existence more widely known, noting that from 2005 to 2010 the general public, attorneys, and health care professionals were unaware of the fund.

Since the program began, the GAO says, some 15,000 people have filed claims. The program's website reports that 3,941 compensation awards have been made, with $2.8 billion awarded. As of 2013, there was $3.3 billion in the fund.

Marcia Cross, director of health care for the GAO and author of the report, said the paperwork accompanying vaccines includes descriptions of potential side effects as well as a mention of the program. But most patients take the word of their doctor, and don't read the accompanying material.

View Images Sophie lies quietly on the living room couch as the family gets ready to enjoy their Sunday activities. She can't talk or communicate much, but her mother sometimes wonders whether, maybe, she understands everything. Photograph by Emily Berl, National Geographic

"Without awareness of the program, individuals who might otherwise receive compensation for a vaccine-related injury or death could be denied compensation because of a failure to file their claim within the statutory deadlines," she said in the report.

When Only Marijuana Helps

On the frontiers of dealing with such a difficult condition, Aquino and Beglinger take solutions wherever they find them. And sometimes that puts them squarely in yet more controversial territory.

Sophie's family has spent thousands of dollars on medical expenses and 24-hour care, most of it performed by the family. Sophie has been on 22 different drugs, in complex combinations. Nothing has helped, Aquino says, except a cannabinoid tincture known as "Charlotte's Web." It has very little THC, so Sophie experiences the calming effect without the high. Now, she only has occasional seizures.

But Sophie still requires help with all of her physical needs and cannot verbally communicate. She turns her face away to show displeasure. She appears to enjoy whatever her father, a chef, prepares, though. And she spends much of her time in her bedroom, where the walls and door are covered in lavender padding to keep her from hurting herself when she butts her head against them.

A wood cutout above her bed says "Miracle." Whenever the family goes to the beach, Sophie makes her desire to go to the water understood. Floating mermaids—in paintings and on pillows and wall hangings—adorn her room.

At Sophie's high school, she attends a special day class for neurologically impaired children. Using an iPad, she communicates a bit, though inconsistently. Aquino says it's impossible to know if she understands much, but she thinks Sophie understands more than is apparent.

"Sometimes, I think she might understand everything. And she's an incredible woman. She has had tens of thousands of seizures, and she still gets up every day," Aquino says.

Aquino, however, says she's tired. She's tired of fighting to get her daughter proper care, to get insurance coverage, to avoid bankruptcy and dismissive doctors. Some doctors are refusing to take patients who aren't vaccinated. But there are doctors who work with cautious parents like Aquino.

Aquino's sons have been getting some, but not all, of their vaccines. Her eldest, Henry, 16, is almost fully vaccinated, but her youngest has more to go. She said that they will receive all of their vaccinations before they travel or head to college.

Jay Gordon, Aquino's doctor, recommends giving vaccines when a child's immune system is strong enough to handle them, and using single-dose vaccines, instead of combined vaccines.

View Images Berlinger, a full-time chef, takes a walk with Sophie before heading off to work. Someone must always accompany her, holding a hand or shoulder. Photograph by Emily Berl, National Geographic

Elizabeth Aquino, 51, is not opposed to vaccines. But when she takes her boys, ages 13 and 16, for a vaccination, it's often years later than most doctors recommend.

Aquino wants no part in the current blame wars, but she says it's definitely time to change the tone of discussion so that parents—whatever their views on vaccinating—don't feel ridiculed and patronized.