Clusters of children without their required vaccinations in about 200 Illinois schools are raising the chances of school-based outbreaks of serious preventable diseases such as measles and whooping cough, a Tribune analysis of state data has found.
The Tribune found that the number of public and private schools with immunization rates below 90 percent — a protection level the state recommends in order to prevent epidemics — has grown dramatically in recent years for each vaccine.
For example, in 2003, 31 schools fell below 90 percent for measles vaccinations. Last year, 124 did. The number of schools below 90 percent for polio rose from 27 to 122 during the same period.
Some of these schools serve low-income students who arrive at school without proof that they are up-to-date on their immunizations, the Tribune found. Others are private schools serving middle-class and wealthy families who sometimes seek religious exemptions from vaccination requirements.
Experts emphasize that the 90 percent vaccination rate is not a magic number separating safe schools from unsafe ones. It's a public health guideline that masks many other factors that can increase or decrease the chance of a school-based outbreak.
But in some schools, the immunization rate against certain diseases fell below 60 percent, the Tribune found, and the number of schools below 90 percent for measles, mumps, polio, rubella or the DTP vaccination more than doubled between 2003 and 2010, from 83 to 198.
Overall, vaccination rates remain high in Illinois schools, at 98 percent. And if the remaining vulnerable students were spread evenly among the state's 5,500 schools, cocooned among the protected, the chances of school-based outbreaks would be extremely low, thanks to an effect known as "herd immunity."
Babies too young to be fully vaccinated and children who cannot be vaccinated for medical reasons rely on this protection, and so do children who have been vaccinated against a disease but don't develop immunity to it.
But scientists and public health officials say clusters of unvaccinated people across the country are weakening the herd immunity made possible through vaccines and resurrecting preventable childhood diseases that can be deadly.
"Whenever the community risk goes up, everyone tends to get affected, including people who are vaccinated," said Saad Omer, an Emory University scientist who researches unvaccinated clusters. "Even the best vaccines are not perfect."
Clusters of unvaccinated people are, Omer said, like patches of dry grass that, with a single match, can start a wildfire that will burn not only dry material, but sometimes wet as well. The match could be a student who returns from a trip abroad with measles or a train commuter with whooping cough.
The U.S. has recorded the highest number of measles cases — 118 through May — since 1996, according to the Centers for Disease Control and Prevention. Most of the cases were linked to people who got measles overseas, and most, but not all, were unvaccinated.
"I don't want to exaggerate the problem. It is not that we are going to have the same rates of measles that we had in the pre-vaccination era any time soon," Omer said. "But the community risk of outbreak goes up, depending on what is happening in your community and in your school. That is why parents should be concerned, even if they do the right thing and get their kid vaccinated."
In a 2008 paper, Omer found clusters of whooping cough cases associated with areas where rates of nonmedical vaccination exemptions were high. "Geographic pockets of vaccine exemptors pose a risk to the whole community," he wrote in the American Journal of Epidemiology.
Experts caution that the state's vaccination records have limits. School staff may err when entering numbers. The information is recorded at the start of the school year, before some students are vaccinated. And some students counted as unimmunized may be up-to-date, or partly so, though they lack the paperwork to prove it.
Still, the records are comprehensive, covering nearly all of the state's schoolchildren, and researchers along with state and federal health officials use the data to track trends and identify pockets of vulnerability should an outbreak occur.
"Despite high overall … compliance levels, outbreaks can still occur when clusters of unvaccinated children congregate together in school and community settings," said Karen McMahon, the Illinois Department of Public Health's vaccination section chief. "Childhood diseases are still very prevalent in the world and can be brought to the U.S. — therefore, vaccination is important."
2 kinds of clusters
At some schools with high rates of unvaccinated children, most or all of the students did not have religious or medical exemptions. They simply arrived at school unimmunized.
That was the case at Passages Charter School in Chicago, where less than 80 percent of children were counted as up-to-date on vaccinations in fall 2010.
Administrator Nicole Feinberg said many of the kids don't have access to regular medical care. Most of her student body comes from low-income families, and almost a third of the students have limited English proficiency, raising translation issues that take time to work out.
By the end of the year, she said, the staff had ensured that nearly all of the kids were up-to-date. "It is extremely important," Feinberg said. "It is quite a bit of work, but we did it."
At Paul Revere Elementary School on Chicago's South Side, where nearly all of the families are low-income, about 20 percent were not fully vaccinated against measles.
Many parents can't read, so understanding and filling out forms can be difficult, said Revere Principal Veronica Thompson. Knowing when a child is due for a shot is another problem.
"Parents are moving frequently, losing paperwork and do not understand the process," she said. "When they have multiple children, some are due for immunizations and others are not. Anything that makes it a tedious process for them really has an impact."
Clusters of unvaccinated students with religious exemptions are more common in private schools, the Tribune found, and such exemptions are rising. For example, religious exemptions for the measles shot grew from about 3,400 in 2000 to about 9,500 last year.
The increase reflects growing unease among some parents — mostly affluent, according to some surveys — about the safety of vaccinations, even though vaccines rarely cause serious complications and the notion that they can cause autism has been scientifically discredited.
Unlike in some states, parents in Illinois wishing to avoid or delay vaccinations for their school-age children cannot obtain philosophical or personal-belief exemptions. Their only option is a religious exemption, but figuring out how to get one is not difficult, as websites such as Vaccination Liberation offer tips and model letters.
At The Einstein Academy, a private school in Elgin, 10 of its 75 students have religious exemptions for most vaccinations, lowering vaccination rates to 86 percent.
Administrator Cathy Ilani said she believes that vaccination is important, but that it's up to the parents to make the decision. "Who am I to question? They are the parents," she said. "I personally feel they are putting their child at risk."
When Dr. Bill Harenburg arrives home after work, he changes his shirt and thoroughly washes his hands before he hugs and kisses his daughters. Some children in his Wheaton pediatric practice are not fully vaccinated, and his infant daughter, Scarlet, is too young to get all of her shots.
Given these precautions, Harenburg and his wife, Aimee, were stunned to find out two months ago that many of the students at Four Winds Waldorf School in Warrenville were not fully immunized. Their daughter Sophia, 11, had just started a 30-day tryout at the school.
Sophia later decided against enrolling. But for as long as she was at Four Winds, the couple instructed Sophia to wash up as soon as she got home.
"Sophia's vaccinated," Aimee Harenburg said. "I was more worried about Scarlet because she's just a baby and she hasn't had all her shots yet."
Four Winds administrator Marianne Fieber said she's not surprised that immunization rates are low at the small private school. The school's nontraditional approach to education attracts people with alternative viewpoints, Fieber said, and some parents believe that getting a preventable childhood disease is safer than getting a shot.
If a student is diagnosed with a vaccine-preventable disease, Fieber said, the school notifies families of children in class with the infected child and with their siblings so parents can take precautions. Three pertussis cases have been reported during her five years at the school, she said.
"There are people who think (not vaccinating) is abhorrent and a disservice to children. They have a right to that opinion," she said. "But we, and some of our parents, think to demand vaccination is also a crime against children."
Dark Age disease
Patty O'Machel, of Deerfield, remembers when her 3-week-old daughter, Shea, began coughing. As the cough worsened, Shea began to vomit and turn blue around her nose and mouth.
Doctors at the hospital delivered a diagnosis. It was pertussis, or whooping cough, a deadly disease in infants that is making a comeback in part because of weakened herd immunity.
Back home, O'Machel said she had to revive her daughter after every coughing fit, thumping the infant on the chest and blowing in her face to get her breathing again. At night, she held Shea's tiny hand as she slept, worrying she would lose her.
Shea stopped coughing, but Patty and her husband slowly realized something was wrong when the girl missed milestones for eating on her own and rolling over. Testing showed Shea had scarring on her brain caused by complications from pertussis. Diagnosed with cerebral palsy, she is cognitively normal but has spasticity in her limbs. At 6 she walks with a walker and braces.
The disease that so affected Shea seemed to O'Machel to come out of nowhere, from a distant past. "Pertussis — that is from the Dark Ages, right?" she said. "Who gets that?"
Strong herd immunity can protect infants and other vulnerable members of society from dangerous diseases, but achieving it requires people to think alike, and they don't.
"Individuals, if they look at the world selfishly, will say: 'I don't want a needle to be stuck into my kid, but I want everyone else to be vaccinated,'" said Dr. Paul E.M. Fine, a community immunity expert and professor of communicable disease epidemiology at the London School of Hygiene and Tropical Medicine. "There is a brutal, ugly logic there."
In some ways vaccines are victims of their own success, said Dr. Evan Anderson, a pediatrician and assistant professor of infectious diseases at Northwestern University Feinberg School of Medicine.
"We as a society have a very short memory," Anderson said. "We forget these life-threatening diseases because we don't see them and haven't seen them in years or potentially during a lifetime."
But that is changing, said Dr. Paul Offit, an infectious-disease specialist, co-inventor of a rotavirus vaccine and author of "Deadly Choices: How the Anti-Vaccine Movement Threatens Us All." Physicians now find themselves treating diseases like measles, mumps and pertussis more frequently, in part because herd immunity is breaking down in places.
"Do we care about the person next to us anymore?" Offit asked.
Measles in our midst
"In this international world, you are one plane flight away from measles," notes Dr. Kenneth Alexander, chief of pediatric infectious diseases at Comer Children's Hospital at the University of Chicago. Some examples:
•In 2008, an unvaccinated Illinois teen returned from a trip to Italy with measles. Public health officials believe the teen sparked an outbreak resulting in 30 cases total across DuPage, Cook and Lake counties. Twenty-five of the 30 cases were unvaccinated children, according to the U.S. Centers for Disease Control and Prevention.
•The same year, an unvaccinated 7-year-old San Diego boy returned from a trip to Switzerland with measles, infecting his two siblings, five children in his school and four kids who had been in his pediatrician's office. Three of the children who caught measles in the pediatrician's office were babies; one wound up in the hospital. All but one of the children older than a year were unvaccinated, according to the CDC.
•This spring, a Minnesota toddler with measles he caught on a trip to Kenya started an outbreak that sickened 19 others, including a months-old baby, according to the CDC. Most were unvaccinated.