What's Really Behind the Measles Outbreak

Medical authorities have been quick to point to the anti-vaccine movement as the cause for the measles outbreak in California, but an analysis of the data suggests there may be other contributing factors, from public health measures that targeted only children to lack of access to medical care.

"One [reason] is active opposition, the other is an access problem," says Dr. Walter Orenstein, professor and associate director at the Emory Vaccine Center.

Though the anti-vaccine movement likely is one of the reasons for the outbreak in California, which so far has spread to 73 residents, a U.S. News analysis of data from the California Department of Public Health show that most of those who currently have the virus are aged 20 or older, meaning some were born not only before the anti-vaccine movement swelled, but also before the U.S. implemented aggressive immunization measures.

These measures have been mostly effective. Today, average rates for the measles-mumps-rubella vaccine – or MMR vaccine – across the country are high, at or above 94 percent among children enrolled in kindergarten.

When narrowed by state, however, the rates vary significantly, from 82 percent in Colorado to 98 percent in Mississippi. According to Barbara Kuter, medical affairs director at Merck Vaccines, which licenses the MMR vaccine, an estimated 85 percent to 95 percent of the population must be vaccinated for best results.

"If I were going to say that I would choose one vaccine that was the most important to prevent the most serious disease – measles would be at the top of my list," says Dr. Kathryn Edwards, professor of pediatrics at Vanderbilt University School of Medicine.

Virus Symptoms and Vaccine
Measles is a virus that begins with a high fever and leads to a runny nose, cough, and red and watery eyes. After a few days, a rash develops and spreads all over the body. People who recover from measles are immune for the rest of their lives, though unlike the flu, there is no specific antiviral treatment for the illness. Care instead is supportive, and includes a focus on hydration and nutrition. Antibiotics can be prescribed in cases where pneumonia or an ear or eye infection develops.

A person with measles is contagious four days before and after a rash appears, meaning someone may have the virus and not know it.

"Measles is a big deal. You don't want to get measles. If you get measles you can die," says Dr. Paul Offit, chief of the division of infectious diseases and the director of the Vaccine Education Center at the Children’s Hospital of Philadelphia.

Patients who contracted measles in California range in age from 7 months to 70 years. The majority of cases were linked to persons who visited or work at Disneyland or Disney California Adventure Park in Anaheim, California.

The virus' qualities make it easy to spread in an environment like Disneyland, which during the winter holidays can reach 70,000 visitors a day. Not only is measles highly contagious – spreading through both direct contact and through the air by coughing and sneezing – but it also remains in the air or on infected surfaces for up to two hours. If one person has it, 90 percent of the people close to that person who have not been vaccinated may also become infected, says the Centers for Disease Control and Prevention.

Two doses of a vaccine are 99 percent effective in preventing infection. According to the CDC, children should get a first vaccine around 12 months and then receive a booster by the age of 6, or before kindergarten. Teens and adults also can get the vaccine if they haven't before – and can discover immunity through a simple blood test.

Most Californians who were infected in the Disneyland outbreak were not vaccinated. As of Friday, the state public health agency had vaccination information on 39 cases. Of those, 32 were unvaccinated and seven were vaccinated.

The majority of the unvaccinated for whom the state public health agency had detailed information were not vaccinated primarily to “personal beliefs," Dr. Gil Chavez, state epidemiologist and deputy director at the Center for Infectious Diseases for the California Department of Public Health, said in an email. She also noted that some were infants younger than 12 months of age who were too young to be vaccinated.

This outbreak follows an already brutal year for the virus, which in 2014 showed a record number of cases since 2000. According to the CDC, 27 states reported 644 cases in 2014, the majority of which were among people who were not vaccinated. Public health agents attributed the spread to travels to the Philippines, which experienced a measles epidemic.

Public Health Measures

Measles vaccines have been available in the U.S. since 1963, but a stronger version was introduced in 1968, Offit says. Up to 4 million Americans contracted measles in the years before the vaccine, and 500 Americans died each year.

The vaccine was so effective that in 1978 the CDC set a goal to eliminate measles in the U.S. by 1982, in part by requiring vaccinations to enter school.

"I would say that the birth of school mandates was associated with the reductions," Offit says.

Two doses of vaccine were not recommended until 1989 – meaning that anyone over the age of 26 today may not have received a booster. Orenstein says the CDC for this reason advises adults traveling outside the U.S. get an MMR vaccine.

According to an article in the Journal of Infectious Diseases, people who were not in the targeted age group went unvaccinated, leaving a gap of people in older age groups who were not protected. "The major problem with measles in highly vaccinated populations occurred among middle school, junior high school, senior high school, and college students," the article read. "The quickest way to eliminate that problem would be a mass revaccination campaign of all such students. This was considered too expensive and logistically difficult to carry out."

Orenstein says the reason public health measures focus on vaccinating younger children is because they suffer the most severe consequences of measles. This approach, however, means some adults could have been missed during that time period. "What I wonder about are these people who fell through the cracks," Orenstein says.

By 1982 the eradication goal was not met, but vaccination drastically reduced the incidence of the disease. Then, in 2000, the U.S. declared that the virus had been eliminated.

Disparities in Care

The fight to eradicate measles did not come without difficulties. Measles resurged from 1989 to 1991, a time Offit remembers well, as it hit Philadelphia particularly hard. More than 55,600 people contracted measles, and 123 died – 90 percent of whom had not been vaccinated.

To what extent children are vaccinated today compared with during this time period is difficult to determine because data are scarce. The CDC didn't begin tracking the percentage of vaccinated children until 1994. By 1995, data show that rates in some states reached a high of 99 percent, and a low of 81 percent.

Previous reports, however, give some clues about vaccination disparities. Many infections during the 1989 to 1991 outbreak were centered in areas where vaccinations levels were low. In fact, the CDC reported: "Surveys in areas experiencing outbreaks among preschool-aged children indicated that as few as 50 percent of children had been vaccinated against measles by their second birthday, and that black and Hispanic children were less likely to be age-appropriately vaccinated than were white children."

The Vaccines for Children Program for Medicaid eligible or uninsured children offers vaccines at no cost. Still, not every child sees a doctor regularly. In 2013, 68 percent of children younger than 6 who were not covered by health insurance had received a well-child check-up in the past year, compared with 92 percent of children who were covered by health insurance.

Some parents also may be delaying vaccinations rather than refusing them outright. "By and large the vast majority of children are immunized, but not all children are immunized, and not all children are immunized in a timely fashion," says Edwards, who is on the committee for infectious disease for the American Academy of Pediatrics. Some parents may opt not to get a series of vaccines all at once, she points out, but that delays the administration of the vaccine.

"There are children not getting immunized for sure – whether they are diverted or too busy or choosing not to do it," she says.

Offit says children can face as many as 26 inoculations or five shots at a time, which prevent 14 different diseases – diseases most parents don't see today.

Anti-Vaccination Movement

Parents refusing or delaying vaccinations likely are a contributing factor to California's outbreak. "I do blame the anti-vaccine movement squarely," Offit says. "It's not your inalienable right to catch and transmit an infection. He adds that patients undergoing chemotherapy, for instance, cannot be vaccinated and become more vulnerable to infection.

The anti-vaccine movement was spurred in 1998, with the release of a report that claimed the MMR vaccine was linked to autism. The findings have been debunked and the lead author lost his medical license, but some parents have remained skeptical as the rates of autism continue to rise at an unprecedented rate, with no known cause.

"We are vaccinating more people than we were 20 years ago," Offit says. "The problem is once you get closer to the ground, some communities have extremely high lack of vaccination, particularly in Southern California."

Offit, who wrote "Deadly Choices" about the anti-vaccine movement, says some Americans have been skeptical of vaccines in general since 1982, over fears about the vaccine to prevent whooping cough. "It was associated with the false concern that the [vaccine] caused permanent brain damage, and created a general scare about vaccines," he says.

The debunked report is still having an effect on public perceptions. A 2010 study from the Pediatric Academic Societies showed that the percentage of parents who delay or refuse vaccines rose from 22 percent in 2003 to 39 percent in 2008.

California as a whole has a high vaccination rate. Data from the state's health department show 90.4 percent of kindergarten students received their immunizations for the 2014 to 2015 school year, a slight difference from the 90.7 percent of children five years earlier. In 2014, 0.19 percent of kindergarten students – the same as the previous year – received medical exemptions, while 2.54 percent received a personal-belief exemption.

But when the data are narrowed, they tell a different story. The American Academy of Pediatrics released a report last year that found five counties had the highest rates of unvaccinated children – from 18 percent to 23 percent among children who turned 36 months old anytime between to 2010 to 2012.

"Parent refusal and delay of childhood vaccines has increased in recent years and is believed to cluster in communities," the report read. "Such clustering could pose public health risks and barriers to achieving quality benchmarks for immunization coverage."

Schools in California mandate that children get vaccinated, but there are personal exemption waivers available that can allow them to decline based on personal beliefs.

According to the National Conference of State Legislatures, Mississippi and West Virginia are the only states that do not allow religious exemptions for vaccinations. Nineteen states allow students to skip vaccines for philosophical objections, which include "moral, philosophical or other personal beliefs." Some states require vaccines only for public school students, while others require them for both public and private schools.

"The issue is trying to help other countries around the world at better immunization," he says.