http://vaccineinfo.net/national_issues/DanishMMRAutismStudy.htm
| Thimerosal: A Missing Link in Denmark MMR-Autism Study
(11/7/02) Today, the New England Journal of Medicine has published an article which refutes a link between MMR and autism using epidemiology. This study was released last week to the major media by the CDC, its major funder along with NAAR. Since then, the CDC PR machine has been working very hard to spin the conclusions their own way. Obviously, they want to put an end to any more discussions and research on vaccines and autism. However, while the study methodology appears to be good, and there is much to learn from the informative findings, there are some significant shortcomings in the conclusions drawn and the study results raise more questions than they answer and underscore the importance for more research. For example, one of the most concerning omissions of the study was their failure to consider the absence of Thimerosal in the other infant vaccines the children of the Danish study received prior to getting their MMR vaccine. Although she did not include it in her article, the reporter from the Dallas Morning News who interviewed me (article below) was able to confirm that the mercury based preservative under so much legal fire for triggering autism was removed from vaccines on the market in Denmark prior to the birthdates of the children studied. American children on the other hand, have potential cumulative mercury exposures at sometimes neurotoxic levels from prenatal exposures including maternal vaccination and immune globulin preparations, environmental pollution and infant vaccinations which create a significantly different set of circumstances when the MMR vaccine, which does not contain mercury, is administered. We feel very strongly that it is erroneous for the study's authors to conclude that since the children in the Danish study did not show an increased incidence of autism after MMR vaccine that the same would hold true for all children. They have not satisfied the question of the MMR vaccine's potential role as a trigger amidst other environmental factors including previously administered mercury containing vaccines that have been given to children outside of their population. It is entirely possible, but not yet studied by the CDC, that a child's immune response, inhibited by the elevated mercury levels from thimerosal-containing vaccinations, has less ability to respond to the measles virus in the MMR vaccine. This might be an explanation for the presence of measles virus cultured from the brains and guts of 80 percent of autistic children. However, we are grateful for their epidemiological research and hopeful that it will spur the absent and yet much needed biological mechanism research here in the United States. Sallie Bernard from Safe Minds (www.safeminds.org) has prepared an exceptional press release and comprehensive point by point assessment of the positives and the negatives of this study. We support and agree with the position of Safe Minds on this study. Additionally, you may want to pick up the November/December issue of Mothering Magazine (www.mothering.com) - it has a sizeable section devoted to investigating Thimerosal and neurodevelomental delays. It includes articles by some of the other brains behind Safe Minds - Lyn Redwood and Liz Birt, articles by mercury expert Dr. Boyd Haley and Autism expert Dr. James Jeffrey Bradstreet , and an interview with Dr. Stephanie Cave. Sincerely, Dawn Richardson Parents Requesting Open Vaccine Education (PROVE) http://vaccineinfo.net -------------------------------------------------------------- Denmark Study on Autism and MMR Vaccine Shows Need for Biological Research Courtesy of Sallie Bernard, Safe Minds (www.safeminds.org) (Cranford, NJ, November 6) The newly released study on autism and the measles-mumps-rubella vaccine ("A Population Based Study of Measles, Mumps and Rubella Vaccination and Autism." New England Journal of Medicine, Vol 347, No 19; Nov 7, 2002: 1477-1483, by Kreesten Meldgaard,et al) is a welcome addition to autism epidemiology. Unfortunately, the study conclusions appear overreaching, claiming that this analysis is the final word on autism and vaccines and implying that more research on the topic is unnecessary. Safe Minds asserts that other vaccines besides MMR may be involved in autism, and that only biological research, not epidemiology, can answer the question of whether the MMR vaccine plays a role in autism. "It is important to note that the study only focused on the MMR vaccine, and not vaccines also implicated in autism which contain the mercury preservative thimerosal," explains Sallie Bernard, executive director of Safe Minds. "The study also failed to investigate whether the MMR vaccine might be interacting with the thimerosal from other vaccines to increase the severity of symptoms in children who already have autism. Finally, the study did not differentiate between regressive autism, which is the type being linked to MMR vaccine, and the more prevalent early onset autism, which is the type being linked to thimerosal." Safe Minds is an advocacy organization which focuses on the role of mercury in neurodevelopmental disrorders, including autism. It was founded by parents of autistic children. Thimerosal contains 50% ethylmercury and has been used in most recommended childhood vaccines, including the Diphtheria-Tetanus-Pertussis (DTP), Haemophilus influenzae type B (HiB), and Hepatitis B (Hep B) vaccines. Research studies have shown that mercury exposure in utero or during early postnatal life - the time when thimerosal vaccines are being given - can cause immune system abnormalities which predispose the child to ongoing viral infections. It is biologically plausible that this immune disruption may have allowed the live measles virus component in the MMR vaccine to persist in susceptible autistic children, making the symptoms of the disorder worse. This connection would not be detected through an epidemiology study like the Denmark one. Nor does the Denmark study have the power to detect differences in rates of regressive autism between vaccinated and unvaccinated children, since the number of regressive cases - estimated to be 10%-20% of all autism cases - would be too small. "The overreaching conclusion of the study should not obscure other important findings from this extensive and well planned analysis from Denmark," continued Ms. Bernard. "The authors report an increased prevalence of autism in that country, and thus it supports other recent studies that are also showing increases. This rise tells us that an environmental agent is at work worldwide that is driving this trend. We believe that thimerosal and environmental mercury - which are worldwide pollutants - are behind the surge. Also, Denmark has had lower and later exposures to thimerosal in vaccines, and the report shows that their rate of autism is lower than in the US, which is also consistent with a thimerosal connection." Safe Minds is encouraged that the Centers for Disease Control sponsored such an extensive study on autism, which shows that this terrible disease is finally getting the attention of public health officials. Safe Minds looks forward to increased support for autism research, especially at the biological level. Assessment of the Denmark MMR-Autism Study (11/6/02) Study "A Population Based Study of Measles, Mumps and Rubella Vaccination and Autism." New England Journal of Medicine, Vol 347, No 19; Nov 7, 2002: 1477-1483. Kreesten Meldgaard, M.D., Andders Hviid, M.Sc., Mogens Vestergaard, M.D., Diana Schendel, P.H.D., Jan Wohlfahrt, M.Sc., Poul Thorsen, M.D., JØrn Olsen, M.D., and Mads Melbye, M.D. KEY MESSAGE This study is well done, but due to its design, it cannot be considered the "definitive" study on autism and the MMR vaccine. Rather, biological research, not epidemiology, is needed to truly answer the question of a link between the MMR and regressive autism. POSITIVE ASPECTS ABOUT THIS STUDY * The CDC and public health authorities are investing dollars and efforts into autism research. These efforts should be applauded, and expanded! * The study reports a steep rise in autism rates from 1980s to 1990s (from <2.0 to >10.0 per 10,000). Increases are also being reported in other countries, again suggesting environmental influences at work, as the recent landmark MIND Institute epidemiology of California study did. * The results appear to support a thimerosal role in the increases in autism being reported in the study in Denmark, and the fact that Danish autism prevalence is less than in the US and the UK, where the thimerosal vaccines are given in larger quantities and/or earlier in life. Further clarification is needed to elucidate this association; specifically, the prevalence by birth cohort and the Danish vaccine schedule and formulations for the time period are needed. * The study authors acknowledge that previous attempts to refute the MMR-autism hypothesis were too poorly designed to reach definitive conclusions. (p.1477, 2nd paragraph on right) * The study brings attention to a rich database of information (i.e., Danish registries) on which additional studies of autism can be based. CAUTIONS ABOUT THE STUDY'S CONCLUSIONS ON BEING THE "DEFINITIVE" STATEMENT ON AUSTISM-MMR * A vaccine-induced autism subset may be present at a much lower prevalence in Denmark since the prevalence of autism is lower in Denmark compared with other countries (see prevalence comparison table at end of document). This may indicate a co-factor effect (e.g. thimerosal) that operates to a greater degree elsewhere. + The lower prevalence in Denmark is not a function of variation in diagnosis, since the same diagnostic criteria developed by CDC was used in Brick, Atlanta, and Denmark. + Means other environmental factors, rates of factors, or combination of factors may be at work in Denmark vs US or UK. + It is possible that MMR increases the rate of autism only when acting in conjunction with another environmental factor, such as mercury. If that factor's prevalence is not controlled for among the study groups (vaccinated vs unvaccinated), it would obscure the role of MMR as a causative factor in the study. + This is entirely biologically plausible since mercury impairs the antiviral immune response, and mercury-exposed fetus and infants are more susceptible to persistent viral infections. + Only psychiatric records were accessed, not medical records, so there were no data on gastrointestinal symptoms and no taking of CSF or GI samples to detect presence or absence of measles virus. Cannot tell if measles persistence is impacting a subgroup of children, if any. Measles persistence may be increasing the severity of autism, even if it is not causing an increase in the number of cases. * There was no attempt to differentiate between regressive and early-onset forms of autism. Since the regressive form comprises a minority of cases - 10%-20% - the power to detect whether there was a difference in regressive autism prevalence between MMR vaccinated and non-vaccinated is lacking in this study. + The assertion that a relative risk of autism of less than one rules out the possibility that there are important subgroups is false. * Although overall well designed, there appear to be some methodological problems with the study, which need further elucidation from the investigators and raise questions about its conclusions of being the "definitive" MMR-Autism study. + The study covered 8 birth cohorts, but two of these, those born in 1997 and 1998, were only 1 or 2 years old when the data records were obtained at the end of 1999. These age groups are too young in most cases to be diagnosed with autism or to be immunized with the MMR. This might have been fine if the impact applied equally to both vaccinated and unvaccinated groups. However, fully half (50.6%) of the unvaccinated group fell into these two younger birth cohorts, vs. just a fourth (27.7%) of the vaccinated group. Therefore, in these 2 birth cohorts, true autism rates will be underestimated (since they have yet to be diagnosed) and unvaccinated status is over-represented. + Children who were in fact vaccinated were assigned to the unvaccinated group if they were diagnosed with autism efore they received the MMR. The reassigned cases comprise 10% of the unvaccinated autism cases (13 out of 130). This commingling blurs the distinction between vaccinated and unvaccinated. It is not clear what effect this would have on the results. + A number of the measures used to arrive at the conclusion that autism and autism disorders were not associated with MMR vaccination are irrelevant. Age of vaccination with MMR, time interval between receipt of MMR and diagnosis of autism, and year of MMR vaccination do not help elucidate the hypothesized relationship between receipt of MMR and development of measles-related symptoms and regressive autism. The age of diagnosis is arbitrary and can vary for many reasons, among them differences in severity of illness, access to care, and clinician skill and preference. Thus these measures cannot be used to refute the presence of a temporal relationship between MMR and onset of symptoms of measles-related illness and regressive autism. * As the authors point out on page 1481, they had no information on the presence or absence of a family history of autism, which could explain the study's negative findings only if families with a history of autism avoided MMR vaccination. It should be noted that in 1993, there was a widely reported news story in Denmark about a parent with autistic twins who asserted that their autism was caused by the MMR vaccine. It is entirely possible that parents with either (a) a family history of autism or (b) an infant or toddler with emerging symptoms of autism, would avoid vaccination at a higher rate than other parents. This would inflate the unvaccinated group with children of families predisposed to autism. A chart showing comparative Reported Rate of Autism from Recent US, UK, and Denmark Studies can be found on the Safe Minds web page at http://www.safeminds.org/assessment/assessment.html. ================================ Danish study: Autism not linked to vaccination 11/07/2002 By SHERRY JACOBSON / The Dallas Morning News http://www.dallasnews.com/latestnews/stories/110702dnnatautism.9ede7.html A major new study of half a million children in Denmark offers further evidence that there is no connection between a common childhood vaccination and the subsequent development of autism. Researchers looked at the incidence of autistic disorders among 440,655 Danish children who had received the standard vaccine to prevent measles, mumps and rubella. Then they compared how often the same disorders appeared in a group of 96,648 children who were not vaccinated. The eight-year study, published Thursday in The New England Journal of Medicine, found the same risk of autism in both groups, providing what the authors called "strong evidence" against the hypothesis that the vaccine could be causing autism. A number of smaller studies in recent years have likewise established no connection. "Few studies can be said to be conclusive, but I think this is as close as we can get," said Dr. Kreesten Meldgaard Madsen, an epidemiologist at the Danish Epidemiology Science Center in Arhus, Denmark, and the study's lead investigator. Eight years of records The study was drawn from the meticulous health records kept of every child born in Denmark from 1991 through 1998. Each childhood vaccination was recorded, as well as subsequent diagnosis of mental disorders such as autism. However, the study is unlikely to satisfy parent groups that have targeted the MMR vaccine as a possible source of their children's medical problems. "This is not going to put the question to rest for parents whose perfectly normal children regressed after they received this vaccination," said Dawn Richardson, president of Parents Requesting Open Vaccine Education, an Austin-based group that includes about 3,500 families concerned about vaccine safety. Such groups point to several smaller studies that have suggested that some children experience behavioral problems soon after receiving a measles, mumps and rubella vaccination at age 18 months. Autism experts have speculated that behavioral difficulties may become apparent at that age but be merely coincidental to the timing of vaccination shots. "Maybe the vaccine is not the cause of autism disorders, but it could be the trigger," Ms. Richardson speculated. "Maybe it's not happening in Denmark, but we're saying there's something going on here in the U.S. with the children who are being vaccinated." Barbara Low Fisher, co-founder and president of another parent group, the National Vaccine Information Center, said a Danish study might not apply to American children. "They are a genetically homogeneous people," Ms. Fisher said of the children in the Danish study. "And we are not." Relevance in U.S.? Dr. Greg Poland, a measles vaccine expert at the Mayo Clinic in Rochester, Minn., agreed that a study in one country might not always relate to people in another. However, he noted that many Americans are of Scandinavian descent. While calling the new study "the single best epidemiological population study done on this issue," Dr. Poland also said that the findings were unlikely to convince people who have decided that vaccinations were harmful for their children. "You can't change emotion or fear-based decisions with scientific data," Dr. Poland said. "It is exceedingly difficult for people not to assume cause and effect in situations like this." He heads the Mayo Vaccine Research Group and is a professor of medicine and infectious diseases at the Mayo Medical School. The combination measles, mumps and rubella vaccine has been in use since 1988, leading some critics to link it to the growing incidence of autism in the United States and elsewhere. Studies have estimated there were two autism cases per 10,000 children ages 5 to 9 in the 1980s and early 1990s. By 2000, the incidence had grown to 10 cases per 10,000 children in the same age group. However, Dr. Madsen and his colleagues noted in the new study that the autism increase in the United States and Denmark "occurred well after the introduction" of the MMR vaccine. "Also, if there were any association between the MMR vaccination and autism, we would expect to see a rise in the diagnoses of autism in the time after vaccination," he said. "We did not see that." |
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