Chavez issued the statement after KQED reported that a Marin County mother had been invited to expose her two young children to a child who had contracted measles. Willis and other health officials suspect the concept of a measles party may have grown out of "pox parties," which were popular in the 1980s, before the chickenpox vaccine was widely available. “People did this with chicken pox all the time,” said Art Reingold, an epidemiology professor at UC Berkeley who worked at the Centers for Disease Control in the 1980s. California public health officials are warning parents against "measles parties," saying that intentionally exposing unvaccinated children to a person with measles could put them at grave risk. “It unnecessarily places the exposed children at potentially grave risk and could contribute to further spread of the outbreak,” the California Department of Public Health said in an email, adding that it “strongly recommends against the intentional exposure of children to measles.” 
 
 Thirty percent of people with measles in the current California outbreak have been hospitalized. Reingold says hosting measles play dates or parties is ill-advised. “We have a safe, effective vaccine, why would you do it?” 
 
 Julie Schiffman says she and her husband are willing to reconsider vaccinating their kids, but no evidence has surfaced to change their minds yet. “When they’re teenagers, I’d say, ‘okay, you have a choice, you can get vaccinated or you can get the measles, what would you rather?’” she said.
– Are "measles parties"—where parents purposely expose unvaccinated kids to infected ones to build up immunity—a good idea? Some parents say yes, but California public health officials say absolutely not, the Los Angeles Times reports. According to a KQED blog post, Marin County mom Julie Schiffman received an invite from another mom to expose Schiffman's two unvaccinated kids to an infected child—she reportedly declined. The underlying reasoning is similar to chickenpox parties held decades ago: Some people believe it's safer for kids to build up "natural immunity" to a weaker form of the disease when they're younger than it is to introduce a vaccine into their bodies. Health officials say that claim is spotty—and dangerous. California state epidemiologist Dr. Gil Chavez says in a statement, "Measles is a serious illness that can have significant consequences," adding that 30% of those with the disease in the current outbreak have been hospitalized. Plus, Marin County Public Health Officer Matt Willis tells the Times, there's no proof immunity obtained naturally is better than vaccine-conferred immunity. Art Reingold, a UC Berkeley epidemiology professor and ex-CDC employee, points out that most "pox parties" took place years ago, before vaccines were widely available. "[Parents thought] this is my opportunity for my kid to get immune the old-fashioned way, the way God intended," Reingold tells KQED, adding, "It's looney tunes" to hold a measles party. Willis notes that while his office hasn't confirmed any measles parties taking place, he's received calls asking about the "benefits" of natural immunity. If scientific advice isn't holding sway, Willis has another suggestion: "Any parents who are considering this ... should have a look at a child who's really sick with measles, and I think they'd change their minds."