When an unvaccinated child in Dr. Daniel Levy's practice came down with whooping cough this year, the Owings Mills pediatrician made a decision: He would no longer see patients whose parents refused to have them immunized against that disease or others, such as measles and meningitis.
The risks posed to his other patients were too great, Levy reasoned. And he felt he couldn't give adequate care to children whose parents rejected some of his most basic advice: That routine childhood vaccines are safe and are the key to preventing diseases that used to kill many before they could reach adulthood.
A new study out today in the journal Pediatrics shows that children who are not vaccinated are 23 times more likely to contract whooping cough - also known as pertussis - than those who have received all of their shots. Lead author Jason M. Glanz, an investigator at the Kaiser Permanente Colorado Institute for Health Research, said he and his colleagues found that, while 1 in 500 vaccinated children came down with pertussis, about 1 in 20 children who were not vaccinated got the disease.
That confirms Levy's fears. "We don't have a large refusal rate in Maryland, but it's something we're really concerned about," he said. "We're going to start seeing the return of diseases we had almost gotten rid of."
Pertussis, which is caused by bacteria, makes children cough uncontrollably. With the cough so hard and so persistent, children often can't catch their breath and they make a "whooping" sound when they attempt to breathe in. Pneumonia or seizures can also develop. There were 64 confirmed cases of pertussis in Maryland last year, including an outbreak of multiple cases in a school and another in a hospital, according to the state health department. That was up from 43 the year before.
A measles outbreak was reported last month in Rockville, with four cases linked to unvaccinated people. Last year, the number of cases of measles in the United States rose to its highest level in a decade.
"The ones who are refusing vaccines are often the epicenters of the outbreaks," said Dr. Daniel Salmon, a vaccine safety specialist with the National Vaccine Program Office at the U.S. Department of Health and Human Services.
State law requires children to get two dozen vaccines against a dozen different diseases from birth to age 5, though parents may object for medical or religious reasons or choose to delay some of the shots. The number who have refused any vaccines for their children has doubled in recent years, though the figure is still under 1 percent, said Dr. Paul A. Offit, chief of infectious diseases at Children's Hospital of Philadelphia and an expert on vaccines.
"We ask a lot and the public generally has responded well," he said.
But there remains a vocal minority who say vaccines are unsafe for children. Some say the large number of shots given to children in a short period of time causes autism - a belief promoted on national television by actresses Jenny McCarthy and Holly Robinson Peete, who blame vaccinations for their sons' autism.
The belief has been rejected by mainstream science, yet it has been widespread enough to make many parents think twice about giving their children so many shots at once. Dr. Robert Sears, son of parenting guru Dr. William Sears, advocates spreading them out.
Meanwhile, there is a generation of parents who didn't see firsthand the devastating impact of the many vaccine-preventable diseases. That allows fear of the vaccine to displace fear of infections, doctors said. Whooping cough is highly contagious and deadly. Prior to the vaccine, pertussis killed about 8,000 people in the United States every year. Now the number is down to about 10.
The vaccine "has kept young children out of the hospital and out of the morgue," said Offit, the author of Autism's False Prophets: Bad Science, Risky Medicine and the Search for a Cure.
Still, pertussis has not been eradicated; it is constantly circulating. Immunity typically wanes in adulthood, so pertussis is more common than most of the other vaccine-preventable diseases. Often, adults pass the disease to their children, who in recent outbreaks have borne the brunt of serious infection, Offit said, just as they did in the pre-vaccination era.
In recent years, health officials have recommended adolescents and adults get a booster shot that includes protection from pertussis.
When there is a decrease in immunizations, Offit said, pertussis is the first disease to come back, making it sort of a proverbial canary in the coal mine.
Most states require children to be vaccinated to enter school, but most allow for exemptions. In Maryland, all a parent has to do to opt out is sign a statement on a school health form that says it is contrary to the family's religious beliefs to be vaccinated.
What can drive an outbreak, doctors say, is when a cluster of parents have refused vaccination for their children.
Offit said he wonders when people will start to realize that the failure to vaccinate puts children at risk - both those whose parents made the decision and those who are unwittingly exposed to disease by the unvaccinated.
"I used to say the tipping point will come when children start to die. But I was wrong," he said. "Now I think it will be when enough children die.
"That vaccines work and are safe is not a question. But people are easily scared. It just seems easier to scare people than to reassure people."
Whooping cough in Md.
Year Total cases Status
2004 159 43 116
2005 219 48 171
2006 153 42 111
2007 118 43 75
2008* 164 64 100
*Data for 2008 are provisional as of May 21, 2009
Sources: Maryland Electronic Reporting and Surveillance System, National Electronic Disease Surveillance System