Furthermore, researchers found that among a group of
parents who were least likely to vaccinate their future children,
some education campaigns actually added to their reservations.
The study's lead author told Reuters Health that the research is an
extension of his work in political science that found it is
difficult to correct people's misinformation.
"We found political misinformation is often very difficult to
correct and giving people the correct information can backfire,"
said Brendan Nyhan, a political scientist at Dartmouth College in
Hanover, New Hampshire.
"We were interested in seeing if the messages public health agencies
were putting out were effective," he said.
Specifically, Nyhan and his colleagues examined public health
campaigns about the measles-mumps-rubella (MMR) vaccine.
Although national U.S. MMR vaccination rates are high, the
researchers write in Pediatrics that there are states where the rate
dips below 90 percent, which is a commonly used threshold for
so-call herd immunity. Herd immunity is the point where high
vaccination rates within a population may also offer protection to
They also write that maintaining high levels of MMR vaccination is
important because of the increasing number of measles cases reported
in the U.S. and recent outbreaks in the UK. Measles is a highly
contagious respiratory disease that can lead to death.
Another study published by Centers for Disease Control and
Prevention (CDC) researchers in the same journal found that
vaccinating U.S. kids born in 2009 according to the routine
immunization schedule will save about $70 billion and prevent over
40,000 early deaths and over 20 million cases of disease.
For their new study, Nyhan and his colleagues used data from
nationally representative surveys conducted in June and July 2011 of
1,759 parents who were at least 18 years old.
During one survey, parents were asked for general information about
the health of their children and about their attitudes toward
The parents were then randomly assigned to receive one of five
messages an average of 12 days later and surveyed again after that.
The first message or campaign used information from the CDC to
correct misinformation that the MMR vaccine causes autism, a belief
that has been disproven.
The second and third campaigns also used materials from the CDC to
present information on the risk of the preventable diseases or a
story about one woman's experience with her son being hospitalized
The fourth campaign consisted of pictures of children who had each
Another group of parents was asked to read information about the
cost and benefits of bird feeding to act as a comparison group.
[to top of second column]
During the second survey, there was no significant increase in
parents' intents to vaccinate their future children, but those who
received the CDC information debunking the link between the MMR
vaccine and autism had fewer misperceptions about that topic.
However, among the one third of people who were least likely to
vaccinate any future children they may have, getting those same
materials was linked to an even lower likelihood that they would
That strengthening of convictions among the least likely to
vaccinate may be due to those people coming up with other arguments
to support their beliefs, the researchers write.
"We can't look inside their head," Nyhan said, adding that it's a
theoretical interpretation but consistent with other research.
The researchers also found the campaigns aimed at stressing the
dangers of the preventable diseases only increased parents'
"We need to test public health messages of all sorts to see if
they're effective — especially with some sub-populations that may be
resistant to some public health messages," Nyhan said.
Dr. Mary Healy said it's also important that there not be just one
mass-market public health campaign addressing vaccines.
"This is very important research, because any public health campaign
we release we have to make sure they're effective," said Healy, from
the Center for Vaccine Awareness and Research at Texas Children's
Hospital in Houston. She was not involved with the new research.
Healy said the study also emphasizes the role of the relationship
between the parent and healthcare provider in clearing up
"If I had any message, you need to talk to your healthcare provider
and bring your worries to your healthcare provider," she said.
Pediatrics, online March 3, 2014.
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