A nice empirical study of vaccine risk communication-and an unfortunate, empirically uninformed reaction to it - Cultural Cognition of Health

Pediatrics published (in “advance on-line” form) an important study yesterday on the effect of childhood-vaccine risk communication.

The study was conducted by a team of researchers including Brendan Nyhan and Jason Reifler, both of whom have done excellent studies on public-health risk communication in the past .

NR et al. conducted an experiment in which they showed a large sample of U.S. parents with children age 17 or under communications on the risks and benefits of childhood vaccinations.

Exposure to the communications, they report, produced one or another perverse effect, including greater concern over vaccine risks and, among a segment of respondents with negative attitudes toward vaccines, a lower self-reported intent to vaccinate any “future child” for MMR (mumps, measles, rubella).

The media/internet reacted with considerable alarm: “Parents Less Likely to Vaccinate Kids After Hearing Government’s Safety Assurance”; “Trying To Convince Parents To Vaccinate Their Kids Just Makes The Problem Worse”; “Pro-vaccination efforts, debunking autism myths may be scaring wary parents from shots”. Etc.

Actually, I think this a serious misinterpretation of NR et al.

The study does furnish reason for concern.

But what we should be anxious about, the NR et al. experiment shows, is precisely the simplistic, empirically uninformed style of risk communication that many (not all!) of the media reports on the study reflect.

To appreciate the significance of the study, it’s useful to start with the distressing lack of connection between fact, on the one hand, and the sort of representations that media and internet commentators constantly make about the public’s attitude toward childhood immunizations, on the other.

The message of these ad hoc risk communicators consists of a collection of dire (also trite & formulaic) pronouncements: a  “growing crisis of public confidence”—an “epidemic of fear,” among a  “large and growing number” of “otherwise mainstream parents”—has generated  an “erosion in immunization rates,” leading, “predictably to the resurgence of diseases considered vanquished long ago.”  “From Taliban fighters to California soccer moms, those who choose not to vaccinate their children against preventable diseases are causing a public health crisis.”

According to the best available evidence, as collected and interpreted by the nation’s most authoritative public health experts, this story is simply false.

Childhood vaccine rates are not “eroding” in the U.S.

Coverage for MMR, for pertussis (“whooping cough”), for polio, for hepatitis-b— all have been over 90% , the national public health target, for over a decade.  The percentage of children whose parents refuse to permit them to receive any of the recommended childhood vaccines has remained under 1% during this time.

Every year, with the release of the latest results of the National Immunization Survey, the CDC issues a press release to announce the “reassuring” news that childhood immunization rates either “remain high” or are “increasing.” “ ‘Nearly all parents are choosing to have their children protected against dangerous childhood diseases,’ ” the officials announce.

There’s definitely been a spike in whooping cough cases in recent years.

But “[p]arents refusing to get their children vaccinated,” according to the CDC, are “not the driving force behind the[se] large scale outbreaks.” In addition to “increased awareness, improved diagnostic tests, better reporting, [and] more circulation of the bacteria,” the CDC has identified “waning immunity “from an ineffective booster shot as one of the principal causes.”

Measles have deemed eliminated in the United States but can be introduced into U.S. communities by individuals infected during travel abroad.

Fortunately, “[h]igh MMR vaccine coverage in the United States (91% among children aged 19–35 months),” the CDC states, “limits the size of [such] outbreaks.” “[D]uring 2001–2012, the median annual number of measles cases reported in the United States was 60 (range: 37–220).”

The “public health crisis” theme that pervades U.S. media and internet commentary dates to the 1998 publication in the British medical journal Lancet of a bogus and since-retracted study that purported to find a link between the MMR vaccine and autism.

The study initiated a genuine panic, and a demonstrable decline in vaccine rates, in the U.K.