A Discredited Vaccine Study’s Continuing Impact on Public Health
By CLYDE HABERMAN
In the churning over the refusal of some parents to immunize their children
against certain diseases, a venerable Latin phrase may prove useful: Post hoc,
ergo propter hoc. It means, “After this, therefore because of this.” In plainer
language: Event B follows Event A, so B must be the direct result of A. It is a
classic fallacy in logic.
It is also a trap into which many Americans have fallen. That is the
consensus among health professionals trying to contain recent spurts of
infectious diseases that they had believed were forever in the country’s
rearview mirror. They worry that too many people are not getting their
children vaccinated, out of a conviction that inoculations are risky.
Some parents feel certain that vaccines can lead to autism, if only because
there have been instances when a child got a shot and then became autistic.
Post hoc, ergo propter hoc. Making that connection between the two events,
most health experts say, is as fallacious in the world of medicine as it is in the
field of logic.
An outbreak of measles several weeks ago at Disneyland in Southern
California focused minds and deepened concerns. It was as if the amusement
park had become the tragic kingdom. Dozens of measles cases have spread2/2/2015 A Discredited Vaccine Study’s Continuing Impact on Public Health NYTimes.com
across California. Arizona and other nearby states reported their own
eruptions of this nasty illness, which officialdom had pronounced essentially
eradicated in this country as recently as 2000.
But it is back. In 2014, there were 644 cases in 27 states, according to the
Centers for Disease Control and Prevention. Should the pace set in January
continue, the numbers could go still higher in 2015. While no one is known to
have died in the new outbreaks, the lethal possibilities cannot be shrugged off.
If the past is a guide, one or two of every 1,000 infected people will not survive.
To explore how matters reached this pass, Retro Report, a series of video
documentaries studying major news stories of the past and their
consequences, offers this special episode. It turns on a seminal moment in
antivaccination resistance. This was an announcement in 1998 by a British
doctor who said he had found a relationship between the M.M.R. vaccine —
measles, mumps, rubella — and the onset of autism.
Typically, the M.M.R. shot is given to infants at about 12 months and
again at age 5 or 6. This doctor, Andrew Wakefield, wrote that his study of 12
children showed that the three vaccines taken together could alter immune
systems, causing intestinal woes that then reach, and damage, the brain. In
fairly short order, his findings were widely rejected as — not to put too fine a
point on it — bunk. Dozens of epidemiological studies found no merit to his
work, which was based on a tiny sample. The British Medical Journal went so
far as to call his research “fraudulent.” The British journal Lancet, which
originally published Dr. Wakefield’s paper, retracted it. The British medical
authorities stripped him of his license.
Nonetheless, despite his being held in disgrace, the vaccineautism link
has continued to be accepted on faith by some. Among the more prominently
outspoken is Jenny McCarthy, a former television host and Playboy Playmate,
who has linked her son’s autism to his vaccination: He got the shot, and then
he was not O.K. Post hoc, etc.
Steadily, as time passed, clusters of resistance to inoculation bubbled up.
While the nationwide rate of vaccination against childhood diseases has stayed
at 90 percent or higher, the percentage in some parts of the country has fallen2/2/2015 A Discredited Vaccine Study’s Continuing Impact on Public Health NYTimes.com
well below that mark. Often enough, these are places whose residents tend to
be well off and well educated, with parents seeking exemptions from
vaccinations for religious or other personal reasons.
At the heart of the matter is a concept known as herd immunity. It means
that the overall national rate of vaccination is not the only significant gauge.
The rate in each community must also be kept high to ensure that pretty much
everyone will be protected against sudden disease, including those who have
not been immunized. A solid display of herd immunity reduces the likelihood
in a given city or town that an infected person will even brush up against, let
alone endanger, someone who could be vulnerable, like a 9yearold whose
parents rejected inoculations, or a baby too young for the M.M.R. shot. Health
professionals say that a vaccination rate of about 95 percent is needed to
effectively protect a community. Fall much below that level and trouble can
Mass vaccinations have been described by the C.D.C. as among the “10
great public health achievements” of the 20th century, one that had prevented
tens of thousands of deaths in the United States. Yet diseases once presumed
to have been kept reasonably in check are bouncing back. Whooping cough is
one example. Measles draws especially close attention because it is highly
infectious. Someone who has it can sneeze in a room, and the virus will linger
in the air for two hours. Any unvaccinated person who enters that room risks
becoming infected and, of course, can then spread it further. Disneyland
proved a case in point. The measles outbreak there showed that it is indeed a
small world, after all.
What motivates vaccineaverse parents? One factor may be the very
success of the vaccines. Several generations of Americans lack their parents’
and grandparents’ visceral fear of polio, for example. For those people, “you
might as well be protecting against aliens — these are things they’ve never
seen,” said Seth Mnookin, who teaches science writing at the Massachusetts
Institute of Technology and is the author of “The Panic Virus,” a 2011 book on
vaccinations and their opponents.
Mr. Mnookin, interviewed by Retro Report, said skepticism about2/2/2015 A Discredited Vaccine Study’s Continuing Impact on Public Health NYTimes.com
inoculations is “one of those issues that seem to grab people across the
political spectrum.” It goes arm in arm with a pervasive mistrust of many
national institutions: the government that says vaccinations are essential,
news organizations that echo the point, pharmaceutical companies that make
money on vaccines, scientists who have hardly been shown to be errorfree.
Then, too, Mr. Mnookin said, scientists don’t always do themselves favors
in their choice of language. They tend to shun absolutes, and lean more toward
constructions on the order of: There is no vaccineautism link “to the best of
our knowledge” or “as far as we know.” Those sorts of qualifiers leave room for
doubters to question how much the lab guys do, in fact, know.
Thus far, the Disneyland measles outbreak has failed to deter the more
fervent antivaccine skeptics. “Hype.” That is how the flurry of concern in
California and elsewhere was described by Barbara Loe Fisher, president of
the National Vaccine Information Center, an organization that takes a dim
view of vaccinations. The hype, Ms. Fisher said in a Jan. 28 post on her group’s
website, “has more to do with covering up vaccine failures and propping up the
dissolving myth of vaccine acquired herd immunity than it does about
protecting the public health.” Clearly, she remained untroubled that most
health professionals regard her views as belonging somewhere in Fantasyland.
© 2015 The New York Times Company