Liz Szabo, USA TODAY -- 8:45 a.m. EST January 23, 2015 The Disneyland measles outbreak, which has grown to at least 50 people in five states and Mexico, is raising questions about state laws that allow unvaccinated children to attend school and stoking heated arguments about vaccination. Most of the cases are in California, according to theCalifornia Department of Public Health. About 25% of the patients were hospitalized, Chavez says. Six of the cases were in infants too young to have been vaccinated. Gil Chavez, deputy director of the California Department of Public Health, says unvaccinated people and families with babies too young to be immunized should avoid crowded places with international travelers, such as theme parks or airports, where measles can spread easily. More than 80% of measles patients in the current outbreak have not been vaccinated. To control the growing outbreak, health officials in Orange County, Calif., where Disneyland is located, told 24 unvaccinated students to stay home for three weeks — the incubation period for measles — after learning that an infected student attended Huntington Beach High School earlier this month. Five Disney employees developed measles after someone with the virus visited Disneyland or the adjacent Disney California Adventure Park between Dec. 15 and Dec. 20. Health officials have not figured out the identity of the patient who started the outbreak. Disney has offered vaccinations and immunity tests to employees "out of an abundance of caution," says Pamela Hymel, chief medical officer at Walt Disney Parks and Resorts. Employees who may have had contact with infected co-workers are being tested for measles and will be on paid leave until they're medically cleared. Containing a measles outbreak is expensive. A 2008 outbreak in San Diego cost taxpayers $10,376 per case to trace contacts and administer vaccinations, according to the Centers for Disease Control and Prevention. While all states require that children receive recommended vaccines before attending school, some make it easier than others to get exemptions. Infectious disease outbreaks are more common in areas with large numbers of unvaccinated students. All states grant exemptions to children for medical reasons, such as immune deficiencies. And all states except Mississippi and West Virginia grant exemptions based on religious objections, according to the National Conference of State Legislatures. Nineteen states, including California, allow students to skip vaccines for philosophical objections. Some states require vaccines only for public school students; other laws apply to public and private schools. California, Oregon and Washington recently made their exemption process more rigorous by requiring "informed refusal." Parents must talk to a health professional about the risks of failing to vaccinate or take an online course before being granted an exemption. Nearly 95% of children are fully vaccinated against measles, according to the CDC. But vaccination rates vary from a low of 82% in Colorado to 98% in Mississippi. Communities need to maintain vaccination rates of at least 92% to prevent measles outbreaks, says Robert Glatter, an emergency physician at New York's Lenox Hill Hospital. Although states set vaccination laws, school districts can grant exemptions, says William Schaffner, a professor at Vanderbilt School of Medicine in Nashville. Some school districts are more permissive than others. In Oregon, more than 7% of schoolchildren are allowed to skip vaccines. In some individual schools, up to 30% of children have been allowed to skip vaccines, Chavez says. "That's a powder keg waiting for a match," Schaffner says. In a phenomenon known as "herd immunity," vaccinated children serve as a "fence" to keep dangerous diseases away from children who can't be vaccinated because of medical problems, such as weak immune systems, Glatter says. In some communities, however, those fences are full of holes. Parents who object to vaccines tend to cluster together in like-minded communities, according to a study published Monday in Pediatrics. That can make measles much easier to spread. Measles was declared eradicated in 2000 in the USA, because it was no longer spreading routinely like colds or the flu. For several years after that, the USA saw only a few dozen measles cases each year, mainly infected travelers who were diagnosed here, according to the CDC. The disease has made a comeback, however, reflecting the influence of huge measles outbreaks abroad as well as pockets of unvaccinated children here. Some parents today hesitate to vaccinate their children, believing the now discredited suspicion that vaccines cause autism. State and federal health officials are urging people to get vaccinated. One dose of measles vaccine given at ages 12 to 15 months prevents 92% of infections, and a second dose at ages 4 to 6 is about 98% effective, Schaffner says. Schaffner says states should make it more difficult for children to get vaccine waivers. One way to do that is for states to require parents to request the waivers every year, rather than giving families a blanket exemption for the duration of a child's school years, says Y. Tony Yang, an associate professor at George Mason University in Fairfax, Va. Others, such as pediatrician Jay Gordon, say states should not make it harder to get vaccine exemptions. Parents who are hesitant about vaccines often feel better if pediatricians or schools give them a choice, he says. Being too strict about vaccine requirements could lead some parents not to vaccinate at all, choosing instead to home school kids or send them to private schools. "If you are coercive at a certain time in a child's life with parents who are hesitant about vaccines, you are going to lose them," says Gordon, of Santa Monica, Calif., who gives vaccines as part of his regular practice. "If you present facts and respect their opinion, you are going to retain herd immunity better" by vaccinating more kids. While there's "no proof the vaccine is dangerous," Gordon says, "it's not a crucial shot." To Gordon, the media are hyping the measles outbreak. "It's someone's absolute right not to vaccinate their kids," Gordon says. "If you haven't vaccinated and you want the vaccine, don't be talked out of it. But don't be talked into it because somebody is telling you that this is an extremely dangerous outbreak." Jaime Friedman, a pediatrician in San Diego, says parents have a responsibility to protect not only their own children but others in the community, too. "It's not just for their own protection," Friedman says. "What if that unvaccinated kid with measles is sitting next to someone who just had chemo? These parents who don't vaccinate don't seem to care about anyone but themselves." Source: Measles outbreak raises question of vaccine exemptions