CDC admits its 2003 study denying mercury autism link was faulty.

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Friday, June 20, 2008

 

 

CDC: Vaccine Study Design "Uninformative and Potentially Misleading"

 

http://cleanupvaccines.blogspot.com/2008/06/cdc-vaccine-study-design-uninformative.htmlDavid Kirby CDC: Vaccine Study Design "Uninformative and Potentially Misleading"Posted June 20, 2008 | 06:43 PM (EST)CDC Dr. Julie Gerberding has delivered a potentially explosive

report to the powerful House Appropriations Committee, in which she

admits to a startling string of errors in the design and methods used

in the CDC's landmark 2003 study that found no link between mercury in

vaccines and autism, ADHD, speech delay or tics.Gerberding was

responding to a 2006 report from the National Institute of

Environmental Health Sciences (NIEHS), which concluded that the CDC's

flagship thimerosal safety study was riddled with "several areas of

weaknesses" that combined to "reduce the usefulness" of the study."CDC

concurs," Dr. Gerberding wrote in an undated mea culpa to Congress,

(provided to me through a Capital Hill staffer) adding that her agency

"does not plan to use" the database in question, the Vaccine Safety

Datalink, (VSD) for any future "ecological studies" of autism.In

fact, Gerberding's report said, any continued use of the VSD for

similar ecological studies of vaccines and autism "would be

uninformative and potentially misleading."Ecological vaccine

studies are large, epidemiological analyses of risks and trends using

computerized data from large populations -- in this case children

enrolled at several big HMOs -- without ever examining a single patient

in person.CDC officials conducted at least five separate

analyses of the data over a four-year period from 1999-2003. The first

analysis showed that children exposed to the most thimerosal by one

month of age had extremely high relative risks for a number of

outcomes, compared with children who got little or no mercury: The

relative risk for ADHD was 8.29 times higher, for autism, it was 7.62

times higher, ADD, 6.38 times higher, tics, 5.65 times, and speech and

language delays were 2.09 more likely among kids who got the most

mercury.Over time, however, all of these risks declined into

statistical insignificance, statistical inconsistency or else outright

oblivion: The relative risk for autism plummeted from 7.62 in the first

analysis, to 2.48 in the second version, to 1.69 in the third round, to

1.52 in the fourth, and down to nothing at all in the fifth, final, and

published analysis printed in the Journal Pediatrics in November of

2003.Vaccine officials attributed the steady drop to the

elimination of "statistical noise" from the data through due diligence

and the endeavor for excellence in governmental statistical analysis.Indeed,

the VSD study was the main pillar of a hugely influential 2004 report

by the Institute of Medicine, which also concluded that there was no

evidence of link between mercury, vaccines and autism.To this

day, public health officials routinely point to five "large

epidemiological studies" representing the "highest quality science,"

none of which found any link to thimerosal.In fact, the

American VSD study has long been held up as the best and brightest of

them all (the others were in Sweden, the UK, and two in Denmark). And

this reputation has stuck in the minds of medicine and the media.Curiously

though, even the study's lead author -- Dr. Thomas Verstraeten, an

employee of vaccine maker GlaxoSmithKline -- protested that the VSD

study "found no evidence against an association, as a negative study

would. In fact, he said that additional study was needed, which "is the

conclusion to which a neutral study must come."That's when Congress stepped in.In

2005, a group of Senators and Representatives headed by Sen. Joe

Lieberman wrote to the NIEHS (an agency of the National Institutes of

Health) saying that many parents no longer trusted the CDC to conduct

independent minded studies of its own vaccine program. Lieberman et al

asked NIEHS to review the CDC's work on the vaccine database and report

back with critiques and suggestions.The final NIEHS report was

a serious and thoughtful critique of where the CDC went wrong in its

design, conduct and analysis of the study. The NIEHS panel "identified

several serious problems," with the CDC's effort, criticism to which

the agency had not responded -- until now.In her letter to the

House Appropriations Committee, the CDC Director responded directly to

many -- though not all -- of the most important criticisms and

recommendations contained in the NIEHS panel report.For

example, the NIEHS had criticized CDC for failing to account for other

mercury exposures, including maternal sources from flu shots and immune

globulin, as well as mercury in food and the environment."CDC acknowledges this concern and recognizes this limitation," the Gerberding reply says.The

NIEHS also took CDC to task for eliminating 25% of the study population

for a variety of reasons, even though this represented, "a susceptible

population whose removal from the analysis might unintentionally reduce

the ability to detect an effect of thimerosal." This strict entry

criteria likely led to an "under-ascertainment" of autism cases, the

NIEHS reported."CDC concurs," Gerberding wrote, again noting

that its study design was "not appropriate for studying this vaccine

safety topic. The data are intended for administrative purposes and may

not be predictive of the outcomes studied."Another serious

problem was that the HMOs changed the way they tracked and recorded

autism diagnoses over time, including during the period when vaccine

mercury levels were in decline. Such changes could "affect the observed

rate of autism and could confound or distort trends in autism rates,"

the NIEHS warned."CDC concurs," Dr. Gerberding wrote again,

"that conducting an ecologic analysis using VSD administrative data to

address potential associations between thimerosal exposure and risk of

ASD is not useful."Read that sentence one more time. The head

of the CDC is saying that its most powerful and convincing piece of

exonerating evidence for thimerosal is, in effect, "useless."I

hope everyone will read it, including the recommendations to make the

VSD better, and the CDC's agreement with all of the suggestions.As

questionable at the US thimerosal study was, "it was an improvement on

other studies, including the two in Denmark, both of which had serious

weaknesses in their designs," Dr. Irva Hertz-Picciotto, Professor of

Public Health at UC Davis Medical School and Chair of the NIEHS panel,

told reporter Dan Olmsted at UPI.That leaves very little for the CDC to go on in terms of proving that thimerosal and autism are not associated in any way.Yes,

there is always the study of disability services data from California

-- which seem to be rising among the youngest cohorts of kids, who

presumably received little or no mercury because thimerosal was largely

removed from childhood shots.But California is an "ecological study" with problems of its own."Although

(this) information is often used by media and research entities to

develop statistics and draw conclusions, some of these findings may

misrepresent the quarterly figures," cautions the website of the

California Department of Developmental Services (DDS). "Increases in

the number of persons reported from one quarter to the next do not

necessarily represent persons who are new to the DDS system."Even

the CDC admits that "there are several limitations" with linking a VSD

study design with the California data, Gerberding wrote to Congress,

because, among other things, California only counts "persons who were

referred to and/or voluntarily entered" the disability system."It

will be interesting to see how the House Committee -- and the

mainstream media -- react to this rather breathtaking confession by the

CDC, which does seem to want to conduct the best vaccine-autism science

possible (see Gerberding's replies to NIEHS recommendations for

improving the VSD: CDC officials are currently conducting in- depth

follow up studies with VSD patients).As the waning months of

the Bush administration get underway, I can't help but wonder if a

little housecleaning might be going on at some of our top health

agencies.(And on that note, please see my blog about the

upcoming HHS/FDA/CDC/NIH workshop on autism triggers in mitochondrial

disorders (ie, Hannah Poling and her five vaccines).

 

 

Posted by

Wayne Rohde

 

 

at

10:32 PM

 

 

 

 

 

 

 

 

 

 

 

 

"It is now 30 years since I have been confining myself to the treatment ofchronic diseases. During those 30 years I have run against so many histories of littlechildren who had never seen a sick day until they were vaccinated and who, in the severalyears that have followed, have never seen a well day since. I couldn't put my finger onthe disease they have. They just weren't strong. Their resistance was gone. They wereperfectly well before they were vaccinated. They have never been well since. "---Dr. William Howard Hay

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