States that easily permit parents to opt out of
vaccinating their children for nonmedical reasons are at
increased risk of pertussis — commonly known as
whooping cough — according to a new study from
researchers with the Johns Hopkins
Bloomberg School of
Public Health, the University of Florida and the
Centers for Disease Control and Prevention. States that
easily grant exemptions or offer personal belief exemptions
have higher nonmedical exemption rates than states that
offered only religious exemptions. The study is published
in the Oct. 11 issue of the Journal of the American
Medical Association.
Pertussis is caused by a bacterial toxin that is
spread easily through person-to-person contact, coughing
and sneezing. It is more severe in infants and young
children, who consequently have a greater risk of
pneumonia, seizures, encephalopathy (a brain disorder) and
other potentially deadly complications. Pertussis, which is
characterized by severe coughing, is endemic in the United
States. The incidence of the disease has increased
nationwide in the last 20 years, with 25,827 cases reported
in 2004, according to the CDC.
"In states that make exemptions widely available or
easy to obtain, there has been an increase in the number of
children who were not immunized, said Saad B. Omer, lead
author of the study and an assistant scientist in the
Bloomberg School's
Department of International Health. "This is a
disturbing trend; previous research has shown that school
immunization requirements have played a major role in
controlling vaccine-preventable diseases in the United
States."
The researchers examined long-term data on state-level
exemption rates at school entry. They also analyzed the
incidence of pertussis for individuals 18 years of age or
younger from 1986 through 2004 for the 48 states that
permit nonmedical exemptions and the District of Columbia.
The study authors found that nonmedical exemption rates
were higher and increasing in states that permitted
exemptions based on personal belief and in states where
exemption processes were less arduous. Those states were
also strongly associated with a higher incidence of
pertussis.
Daniel Salmon, senior author of the study and an
associate professor of epidemiology in the University of
Florida's College of Medicine, said, "Our results add a new
piece of information in our effort to control pertussis. A
reduction in the number of U.S. children receiving school
immunizations hinders one of our most effective methods in
preventing outbreaks of vaccine-preventable diseases,"
added Salmon, who is also an adjunct associate professor in
the Bloomberg School's Department of International
Health.
In their study, the researchers propose that a balance
be struck between parental autonomy and public health
mandates. Not only should public vaccine information
campaigns be directed at parents who have real concerns,
but exemptions should be more difficult to obtain, they
said.
In a May 2005 article published in the Archives of
Pediatrics and Adolescent Medicine, Salmon and
colleagues reported that parents who requested immunization
exemptions perceived vaccines to be unsafe and ineffective,
despite strong scientific evidence to the contrary. They
also believed their children were less susceptible to
vaccine-preventable diseases and that the diseases were
less severe. Parents of exempt children also had low levels
of trust for the government.
The study, partially funded by a grant from the
Centers for Disease Control and Prevention, was co-authored
by Omer, William K. Y. Pan, Neal A. Halsey, Shannon
Stokley, Lawrence H. Moulton, Ann Marie Navar, Mathew
Pierce and Salmon. The co-authors have received payment for
consultant work or testimony unrelated to the current study
on behalf of Sanofi Pasteur, GlaxoSmithKline, Merck, Chiron
and the U.S. Department of Justice.