TUESDAY, Oct. 10, 2006 (HealthDay News) -- More parents are refusing to have their children immunized against common childhood diseases, as some states make it easier to evade mandatory requirements.
The result is a higher incidence of pertussis -- whooping cough -- among their children, a nationwide study finds.
Every state allows medical exemptions to immunizations, and 19 now allow exemptions based on personal beliefs. This has led to a mean exemption rate increase of 6 percent a year in the number of children not being immunized, from 0.99 percent in 1991 to 2.54 percent in 2004, said researchers at the Johns Hopkins Bloomberg School of Public Health.
"Pertussis incidence in states allowing personal belief exemptions was twice as high as in states that only offered religious exemptions," the researchers reported.
The findings are published in the Oct. 11 issue of the Journal of the American Medical Association.
Pertussis can be a serious disease. There are more than 10,000 cases in the United States each year, and 13 children died of it in 2003.
Pertussis was chosen for the study because "it is a relatively common preventable disease that has had a vaccine for a long period of time now and still is not eradicated in the United States," said atudy author Dr. Saad B. Omer, associate director of Hopkins' Institute for Vaccine Safety.
The study shows that easier exemption rules "play a significant role" in the increased incidence of the disease, Omer said. "It is increasing in states that most easily allow exemptions."
State-mandated immunization programs have virtually eliminated childhood diseases that once were commonplace. In the first two years of life, a child can get up to 24 injections, for vaccines against measles, mumps, rubella, pertussis, polio, diphtheria, tetanus, hepatitis A, hepatitis B, pneumonia, and influenza type B, among others.
The rise in requests for exemptions is, in large part, due to the success of the immunization program, the researchers said.
"The success of immunizations has paradoxically shifted many parents' concerns from the risks of vaccine-preventable diseases to the risks of vaccine-adverse events," they said.
This is not the first report of increased rates of a childhood disease due to parents' refusal to immunize children, said Dr. Paul A. Offit, chief of infectious diseases at the Children's Hospital of Philadelphia. An earlier report showed the same effect with measles, he said.
Refusal to have children immunized appears to be a peculiarly American phenomenon, Offit said, caused by "the balance we have in this country between individual rights and the rights of the public. To my knowledge, this is the only country to have state mandates for immunization, and the only one that needs them."
Studies have shown that 10 percent to 15 percent of American parents have doubts about the safety of vaccines, Offit said. "What this paper says is that you can go too far. If you refuse to get a vaccine, it affects not only you and your child but also the person in school next to your child," he said.
The danger of infection is increased because "people who refuse to have a child immunized are not evenly distributed in the country or in the states," said Dr. Robert S. Baltimore, a professor of pediatrics and immunology at Yale University School of Medicine, and a member of the American Academy of Pediatrics' committee on infectious diseases. "There are clusters," he added.
"People think that if they avoid vaccination, they will be protected by people who get vaccinated," Baltimore said. "That is not true. They share in the community concepts, which make it more probable that the neighbors have avoided vaccination."
The new report may help change some parents' and politicians' views on vaccine-exemption policies, Baltimore said. "State policy is often influenced by anti-vaccination groups who are well organized," he said. "This paper may counter their influence."
Offit said: "We get a lot of calls from parents who are troubled by vaccines. Then there is an unmovable group that believes it is a conspiracy of doctors and pharmaceutical companies, that it is all about selling vaccines. No matter what the data shows, they are not convinced. We have to ask people to have faith, and there has been an erosion of it."
For more on childhood immunizations, visit the American Academy of Pediatrics.