Messages designed by public health
officials to debunk parents' misconceptions about a causal link between vaccines and autism may have had an opposite effect, discouraging immunization instead.
A study published online this week in the journal Pediatrics
found that interventions traditionally used to encourage parents to vaccinate their children did nothing to increase their intent to get them inoculated with mumps, measles and rubella vaccine.
More than 1,700 parents were surveyed between June and July of 2011 for the study, which randomly assigned them one of four messages. One included information explaining the lack of evidence to support that MMR vaccine caused autism, while another showed images of children inflicted with the diseases that MMR is designed to prevent.
The message explaining the lack of evidence surrounding an alleged link between vaccine and autism was found to have helped to reduce parents' misconceptions, but only decreased the intent to immunize among those with the most negative views on vaccines.
Among those parents who received the message with the images of children affected with the vaccine-preventable diseases, belief in a vaccine-autism link only increased, according to the study.
“Current public health communications about vaccines may not be effective,” the study concluded. “Attempts to increase concerns about communicable diseases or correct false claims about vaccines may be especially likely to be counterproductive.”
Diseases such as measles that once killed hundreds and infected thousands each year were all but eliminated by 2000 because in large part to yearly vaccination requirements for schoolchildren.
But cases of measles have been rising in recent years in areas of the country where child immunization rates have fallen below levels needed to achieve “herd immunity,” where the number of those vaccinated is high enough to maintain public safety against infection for the entire population.
In 2013, the number of reported cases of measles in the U.S. was nearly three times the annual average of 60, according to the Centers for Disease Control and Prevention
. The majority of outbreaks of the disease that occur can be traced to people who contracted the disease outside the U.S. and brought it into this country who spread the disease to people who were not vaccinated, experts say.Follow Steven Ross Johnson on Twitter: @MHsjohnson