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How and why does history get rewritten?

If you read a history book written in the United States from the 1950s, on the origins of the Cold War, you'd get a definitive answer on which country was to blame, backed up with extensive evidence to justify its points. The book would say it was the fault of Soviet Russia, under the leadership of Stalin, and it would refer to Stalin's takeover of eastern Europe, his refusal to grant its governments the democracy he had promised them, and his desire to spread communism to all corners of the globe. His truculence at the 1945 Potsdam Conference, his execution of anyone who stood in his way, and his perfidy over Berlin would all be stated effusively. Historians who viewed the Cold War in this way have become known as 'Orthodox' thinkers.

If you picked up a US history book from the late 1960s, the chances are, you'd get a very different view. You'd read of America's desire to take over economic control of Europe and tie the countries there to the dollar. You'd read of Truman's aggressiveness at the Potsdam Conference, his use of the atomic bomb (was the second one actually necessary, or was it just a warning to the Soviets?), the setting up of NATO; in short, you'd be told that responsibility for the Cold War was Washington's, and that Stalin merely acted defensively, after having lost around 25 million people as a result of the Second World War. This way of approaching the Cold War was termed 'Revisionist'.

By the 1980s and 1990s, the story would be retold again. Historians would point out that the Cold War was inevitable, given the ideological differences that existed between East and West, and it is futile to try to blame one person or even one country in particular. Did the Cold War even start in 1945? Is it not more correct to trace its origins back to 1917 and the Russian Revolutions? Better still, why not to the publication of Marx's works in the 19 th century? Or even to the conditions that inspired him? This school of thought was given the name 'Post Revisionism'.

The point is, that our retelling of what happened in the past changes constantly, and this is true with just about every major event in history. The causes of the Second World War used to be straightforward. Hitler was to blame. But then along came the British historian AJP Taylor, and iconoclastically revised our view by suggesting that Hitler was only doing what he was allowed to do, and the blame for the war should be levelled at the policy of appeasement, in which the British and the French gave away large chunks of Europe to him to keep him happy. Historians seemed to reach a consensus on the causes of the First World War by the 1960: it was more or less agreed that blame should be shared between the major powers of Europe, and that all had a part to play in the outbreak of fighting in 1914. But then Fischer came along, and suggested (much to the horror of his countrymen) that Germany alone was to blame, that they had intentions of taking over the whole of Europe, and that in encouraging Austria to attack Serbia in retaliation for the assassination of Archduke Franz Ferdinand, they had set in motion a series of events that they knew would lead Europe into major conflict.

So what affects our interpretation of the past, and why does it get rewritten? The following overlapping factors all affect the way in which history may be approached, and mean that it will inevitably be written from different perspectives, and change over time.

The availability of evidence for the historical account

The first of these factors is pretty straightforward. Everything we write about the past is based on evidence, and if we use different evidence, we will inevitably arrive at a different version of what happened in the past. Historians should, of course, use as much evidence as possible, and the evidence should be as varied and widespread as possible, to avoid building up a biased picture of the past. But sometimes they are not always able to access evidence, which later becomes available to other historians. Using the example above, following the collapse of the Soviet Union in 1991, a huge range of archives, previously hidden behind the dreaded 'Iron Curtain' were made accessible, and historians were able to examine a lot more evidence on what – and who – caused the Cold War.

Certain documents revealed more about the conditions within Russia, leading one of the most famous Cold War historians, John Lewis Gaddis to harden his post-revisionist approach on who was responsible. Learning more about Stalinist Russia led him to conclude that Stalin was more able to compromise than Truman, the President of the United States, who couldn't afford to look soft on the communists. Writing in 1997, Gaddis' said ( We Now Know, Rethinking the Cold War):

World politics was an extension of Soviet politics, which was in turn an extension of Stalin's preferred personal environment: a zero-sum game, in which achieving security for one meant depriving everyone else of it.

The level of objectiveness used by the historian in choosing the evidence

But sometimes a wide range of evidence is available, but historians choose not to use it. Instead, they are so keen to prove a hypothesis that they have developed, that they are unwilling to consider evidence that might contradict what they believe. They may not do this consciously – sometimes after a historian feels that she has answered a question, they cease looking for the answer (contradicting Socrates' dictum about never ceasing to ask questions in order to discover the truth), feeling, perhaps, that the answer fits in well with their wider paradigm. Sometimes, though, they may be very aware that they are fitting the facts around a theory, rather than the other way around, which is a guaranteed route to arriving at a false picture of the world. This is the approach of historians who have a specific purpose to history writing, rather than just investigating what happened, or are affected by the paradigm through which they view the world (see the sections below).

One example of using evidence selectively is the Marxist account of the start of the First World War. For Marxists, everything in history can be explained by class conflict, so the reason for the First World War kicking off had to be the same. Lenin decided to focus on the colonial conflicts that were going on in Africa and other parts of the world, as the European states tried to build up their back yards bigger than their neighbours, and enrich themselves as much as possible. He said that the war was just an extension of this colonial conflict, as capitalists tried to extend their markets even further.

Unfortunately, Lenin focused far too much on the colonial issues, and neglected other aspects that had nothing to do with class, such as the rise of nationalism and militarism in Europe. Indeed, most historians now play down the role played by the colonial conflicts, stressing that capitalists were now investing their money in non-colonial areas (such as the USA).

It seems that Lenin was far too wrapped up in his communist outlook of the world to see that other possible explanations existed for the start of the war.

The purpose of the historical account

As soon as there is a purpose other than trying to tell the truth about what happened in the past (regardless of whether it is possible to find out the truth), a historical account becomes tainted. This sounds easy to avoid at first sight – just tell the truth about what happened! – but in practice, very few of us are able to be so removed and objective. There are often other motives for doing things. For the historian, these other motives may be academic ambition (radical new theories on why an event happened always make a big intellectual impact), money (history books can be bestsellers, and get their authors into the popular press), to forward an ideological position, attack or defend a government, or toe the political line of the nation in which the history account is written.

The most obvious examples of this last factor would be works of propaganda to consolidate the position of a dictator: both Hitler and Stalin 'rewrote' history to portray their struggles to gain power as being inevitable, glorious, and popular, but such a manipulation of the facts is a feature of all authoritarian states. As George Orwell observed, 'he who controls the past, controls the future, he who controls the present, controls the past.'

But this phenomenon isn't only a characteristic of one-party states. School textbooks in democratic states are often selective in their use of evidence in order to present a country in a good light. Japan, which has struggled to accept its recent past, is one example of a nation in which certain groups have tried to whitewash more painful events in order to clean up the country's image. The Japanese Society for History Textbook Reform is one such group, and in 2000 they managed to influence the content being put into a textbook to downplay Japan's aggressiveness in the 1930s. The resulting scandal led to the book being rejected by many school boards, unwilling to compromise their teaching of the subject.

Social, political, and psychological paradigms at the time of the historical account

It's very hard to escape the influence of the prevailing political and social climate, and this is true for historians as much as for anyone else. How we see and understand the world inevitably depends on the intellectual fashions of the time, and it takes an unusually courageous mind to break free from such constraints.

The good news is that we can often learn just as much about history from the way history is told as from the events that are being covered. To put this in context, have a look again about what has just been said about different accounts of the Cold War. You have the orthodox view, the revisionist view, the post-revisionist view, and, if we include the changes that occurred after the collapse of the Soviet Union, the post-1991 view.

Apart from the last of these, it's hard to imagine why accounts developed like this. But study the history of when each view was being developed, and you soon understand why the different ideas took hold.

The orthodox account appeared just after the Second World War. The USA and her allies had just fought in the most catastrophic conflict in history, and the events were still fresh in people's minds. Patriotism and allegiance to one's country were still strong, and no-one was yet willing to question the role of governments and politicians who had defended the free world, safeguarded families and societies, and, importantly, were still very much alive and in charge. Therefore, the view that the USA could have been responsible for starting a new conflict was unthinkable and unacceptable. The Cold War could only have been an initiative from the other side, or the USSR. Although Churchill's famous speech in Fulton, Missouri in 1946, in which he said:

From Stettin in the Baltic to Trieste in the Adriatic an "iron curtain" has descended across the Continent. Behind that line lie all the capitals of the ancient states of Central and Eastern Europe. Warsaw, Berlin, Prague, Vienna, Budapest, Belgrade, Bucharest and Sofia; all these famous cities and the populations around them lie in what I must call the Soviet sphere, and all are subject, in one form or another, not only to Soviet influence but to a very high and in some cases increasing measure of control from Moscow.

His speech was condemned by many governments of the day, but it took hold in the imagination of ordinary people, and academics (who held him in great esteem), and informed the way they viewed what was going on.

Times change, though. The Americans soon showed themselves willing to combat the threat of communism (as they saw it) using any means at their disposal. This started at home, and in the Red Scare of the 1950s fuelled by Senator McCarthy, it seemed for a time that the USA had become the authoritarian menace that it said it was struggling against. Then came Vietnam, a brutal conflict in which the Americans no longer to be wearing the white hat of the hero. People now questioned their government, and academics were in the forefront of this soul-searching. It became acceptable, moral, even, to realign your allegiance, and accept that there were other perspectives. Perhaps the USSR had just been acting defensively. Perhaps it was the USA that had deliberately enflamed the situation.

The post-revisionist standpoint partly developed as an logical intellectual extension of the debate, but there is little doubt that it was influenced by the negative feelings towards the Soviet Union during the 1970s and early 1980s which saw such events as the invasion of Afghanistan and the persecution of political opponents who spoke out against the ailing regime. The new thinking was that there was little to choose between these two powers, and that to a large degree, the struggle was inevitable result of the ideological differences between them. Ernest May in 1984 typified this approach by writing ( From American History, A Survey, by Alan Brink, published in 1986):

After the Second World War, the United States and the Soviet Union were doomed to be antagonists.... There probably was never any real possibility that the post-1945 relationship could be anything but hostility verging on conflict... Traditions, belief systems, propinquity, and convenience ... all combined to stimulate antagonism, and almost no factor operated in either country to hold it back.

The method used by the historian

Historians often have different approaches to history, and contrasting methods lead to different results. Going way back to the Greeks, and looking at the two men who are sometimes called the first historians, we can see that different methods were used from the very beginning of history-telling. In the 5 th century BC, Herodotus set out to explain the origins of the long war between the Greeks and the Persians. Although he drew on an admirable range of academic disciplines, considering geography, anthropology, and natural sciences (as we would call these today), he was not afraid of drawing on accounts that came from before living memory, and incorporated rumour into his theorising.

In contrast, Thucydides, writing around the same time, and trying to analyse the Peloponnesian wars between Athens and Sparta, had a stricter approach. He focused on political and military factors rather than digressing into other areas, and stuck to living memories, and was often sceptical in his judgement of opinions he encountered. The result is that his history is .

In more modern times, the same principle applies. historians have to remain as objective and sceptical as possible, and if they don't, their results can suffer. In 1983, a German magazine Der Stern published extracts of what it claimed were the never-before-seen diaries of Adolf Hitler.

The world's media went into a frenzy. Everyone wanted to publish their own version of the story, which would mean, of course, paying large amounts of money for the diaries from Der Stern. In Britain, the highly-respected Sunday Times newspaper hired the Second World War specialist Hugh Trevor-Roper to verify the diaries before the newspaper put in a bit. He flew to Switzerland, and announced in an article for the paper:

I am now satisfied that the documents are authentic; that the history of their wanderings since 1945 is true; and that the standard accounts of Hitler's writing habits, of his personality and, even, perhaps, of some public events, may in consequence have to be revised.

But Trevor-Roper, possibly affected by his position of power and his sudden emergence as the most famous historian in the world, had been tricked. Forensic experts, examining the diaries, quickly concluded that not only were the diaries fake, they were rather poor fakes at that. The editors of Der Stern and the Sunday Times resigned, and Trevor-Roper's reputation was never the same again. The forger, Konrad Kujau, served three years in prison, although he emerged as a minor celebrity, and had some success in selling 'genuine Kujau fakes'.

Different outlooks on the nature of history

Historians differ not just in terms of their method, but also in terms of their philosophical approach to history. Some embrace the Nietzschean idea that there is no truth, only our interpretation of it, something that is probably easier to apply to the past than to the present. Some maintain that it is possible to come close to a retelling of what actually happened, as long as one follows a strict method in accessing it. This will be discussed in the next section.

Another difference in outlook is in what determines the unfolding of events in the past. Is history shaped by forces that influence our society, as Durkheim and social scientists who follow a holistic approach would have it, or is it determined by the actions of individuals? A bitter argument occurred in the 1960s and 1970s between two eminent British historians on this very matter, and their different outlooks on history represent one of the central debates in how we 'do' history and view the past. EH Carr, who specialized in Russian history, wrote a famous book in 1961 called What is History? The book summed up his ideas on history, which forwarded the idea that a more sociological approach should be used when understanding past events. On the other hand, Geoffrey Elton, the Cambridge Tudor historian was equally trenchant in his views. His book, written 6 years after What is History?, and designed as a riposte to it, was The Nature of History. In it, he defended a scientific approach to the subject in which the actions of individuals are the defining engines of historical development. He was also very opposed to the use of other disciplines to further our understanding in the subject.

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How and why does history get rewritten? - theoryofknowledge.net

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If you read a history book written in the United States from the 1950s, on the origins of the Cold War, you'd get a definitive answer on which country was to blame, backed up with extensive evidence to justify its points.

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How Science Changes

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The history of science and the history of the scientific disciplines

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The history of science is full of great works that have marked a turning point in the development of a branch of knowledge, and in which the proposals for a new theoretical frame of reference or a new systematization of the known facts were preceded by an extensive historical introduction consisting in the evolution of the topic up to that moment.

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How Knowledge of Medicine Changes

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Abstract

Although child vaccination rates remain high, some parental concern persists that vaccines might cause autism. Three specific hypotheses have been proposed: (1) the combination measles-mumps-rubella vaccine causes autism by damaging the intestinal lining, which allows the entrance of encephalopathic proteins; (2) thimerosal, an ethylmercury-containing preservative in some vaccines, is toxic to the central nervous system; and (3) the simultaneous administration of multiple vaccines overwhelms or weakens the immune system. We will discuss the genesis of each of these theories and review the relevant epidemiological evidence.

A worldwide increase in the rate of autism diagnoses-likely driven by broadened diagnostic criteria and increased awareness-has fueled concerns that an environmental exposure like vaccines might cause autism. Theories for this putative association have centered on the measles-mumps-rubella (MMR) vaccine, thimerosal, and the large number of vaccines currently administered. However, both epidemiological and biological studies fail to support these claims.

MMR

On 28 February 1998, Andrew Wakefield, a British gastroenterologist, and colleagues [ 1] published a paper in The Lancet that described 8 children whose first symptoms of autism appeared within 1 month after receiving an MMR vaccine. All 8 of these children had gastrointestinal symptoms and signs and lymphoid nodular hyperplasia revealed on endoscopy. From these observations, Wakefield postulated that MMR vaccine caused intestinal inflammation that led to translocation of usually nonpermeable peptides to the bloodstream and, subsequently, to the brain, where they affected development.

Several issues undermine the interpretation by Wakefield et al. [ 1] of this case series. First, the self-referred cohort did not include control subjects, which precluded the authors from determining whether the occurrence of autism following receipt of MMR vaccine was causal or coincidental. Because ∼50,000 British children per month received MMR vaccine between ages 1 and 2 years-at a time when autism typically presents-coincidental associations were inevitable. Indeed, given the prevalence of autism in England in 1998 of 1 in 2000 children [ 2], ∼25 children per month would receive a diagnosis of the disorder soon after receiving MMR vaccine by chance alone. Second, endoscopic or neuropsychological assessments were not blind, and data were not collected systematically or completely. Third, gastrointestinal symptoms did not predate autism in several children, which is inconsistent with the notion that intestinal inflammation facilitated bloodstream invasion of encephalopathic peptides. Fourth, measles, mumps, or rubella vaccine viruses have not been found to cause chronic intestinal inflammation or loss of intestinal barrier function. Indeed, a recent study by Hornig et al. [ 3] found that the measles vaccine virus genome was not detected more commonly in children with or without autism. Fifth, putative encephalopathic peptides traveling from the intestine to the brain have never been identified. In contrast, the genes that have been associated with autism spectrum disorder to date have been found to code for endogenous proteins that influence neuronal synapse function, neuronal cell adhesion, neuronal activity regulation, or endosomal trafficking [ 4].

Although no data supporting an association between MMR vaccine and autism existed and a plausible biological mechanism was lacking, several epidemiologic studies were performed to address parental fears created by the publication by Wakefield et al. [ 1] ( table 1). Fortunately, several features of large-scale vaccination programs allowed for excellent descriptive and observational studies-specifically, large numbers of subjects, which generated substantial statistical power; high-quality vaccination records, which provided reliable historical data; multinational use of similar vaccine constituents and schedules; electronic medical records, which facilitated accurate analysis of outcome data; and the relatively recent introduction of MMR vaccine in some countries, which allowed for before and after comparisons.

Ecological studies.Researchers in several countries performed ecological studies that addressed the question of whether MMR vaccine causes autism. Such analyses employ large databases that compare vaccination rates with autism diagnoses at the population level.

1. In the United Kingdom, researchers evaluated 498 autistic children born from 1979 through 1992 who were identified by computerized health records from 8 health districts [ 5]. Although a trend toward increasing autism diagnoses by year of birth was confirmed, no change in the rates of autism diagnoses after the 1987 introduction of MMR vaccine was observed. Further, MMR vaccination rates of autistic children were similar to those of the entire study population. Also, investigators did not observe a clustering of autism diagnoses relative to the time that children received MMR vaccine, nor did they observe a difference in age at autism diagnosis between those vaccinated and not vaccinated or between those vaccinated before or after 18 months of age. These authors also found no differences in autism rates among vaccinated and unvaccinated children when they extended their analysis to include a longer time after MMR exposure or a second dose of MMR [ 6].

2. Also in the United Kingdom, researchers performed a time-trend analysis using the General Practice Research Database-a high-quality, extensively validated electronic medical record with virtually complete vaccination data [7]. More than 3 million person-years of observation during 1988-1999 confirmed an increase in autism diagnoses despite stable MMR vaccination rates.

3. In California, researchers compared year-specific MMR vaccination rates of kindergarten students with the yearly autism case load of the California Department of Developmental Services during 1980-1994 [8]. As was observed in the United Kingdom, the increase in the number of autism diagnoses did not correlate with MMR vaccination rates.

4. In Canada, researchers estimated the prevalence of pervasive developmental disorder with respect to MMR vaccination in 27,749 children from 55 schools in Quebec [9]. Autism rates increased coincident with a decrease in MMR vaccination rates. The results were unchanged when both exposure and outcome definitions varied, including a strict diagnosis of autism.

Additional population-based studies considered the relationship between MMR vaccine and the "new variant" form of autism proposed by Wakefield et al. [1]-specifically, developmental regression with gastrointestinal symptoms. Although it is difficult to analyze such a phenomenon when it is unclear that one exists (which complicates the formulation of a case definition), conclusions may be gleaned from the data with respect to developmental regression alone (i.e., autism irrespective of coincident bowel problems).

1. In England, researchers performed a cross-sectional study of 262 autistic children and demonstrated no difference in age of first parental concerns or rate of developmental regression by exposure to MMR vaccine [10]. No association between developmental regression and gastrointestinal symptoms was observed.

2. In London, an analysis of 473 autistic children used the 1987 introduction of MMR to compare vaccinated and unvaccinated cohorts [11]. The incidence of developmental regression did not differ between cohorts, and the authors observed no difference in the prevalence of gastrointestinal symptoms between vaccinated and unvaccinated autistic children.

Two conclusions are evident from these data. First, the explicit consideration of developmental regression among autistic children does not alter the consistent independence of MMR vaccine and autism. Second, these data argue against the existence of a new variant form of autism.

Retrospective, observational studies.Four retrospective, observational studies addressed the relationship between MMR vaccine and autism.

1. In the United Kingdom, 71 MMR-vaccinated autistic children were compared with 284 MMR-vaccinated matched control children through use of the Doctor's Independent Network, a general practice database [12]. The authors observed no differences between case and control children in practitioner consultation rates-a surrogate for parental concerns about their child's development-within 6 months after MMR vaccination, which suggests that the diagnosis of autism was not temporally related to MMR vaccination.

2. In Finland, using national registers, researchers linked hospitalization records to vaccination records in 535,544 children vaccinated during 1982-1986 [13]. Of 309 children hospitalized for autistic disorders, no clustering occurred relative to the time of MMR vaccination.

3. In Denmark, again using a national registry, researchers determined vaccination status and autism diagnosis in 537,303 children born during 1991-1998 [14]. The authors observed no differences in the relative risk of autism between those who did and those who did not receive MMR vaccine. Among autistic children, no relationship between date of vaccination and development of autism was observed.

4. In metropolitan Atlanta, using a developmental surveillance program, researchers compared 624 autistic children with 1824 matched control children [15]. Vaccination records were obtained from state immunization forms. The authors observed no differences in age at vaccination between autistic and nonautistic children, which suggests that early age of MMR vaccine exposure was not a risk factor for autism.

Prospective observational studies.Capitalizing on a long-term vaccination project maintained by the National Board of Health, investigators in Finland performed 2 prospective cohort studies. Researchers prospectively recorded adverse events associated with MMR-vaccinated children during 1982-1996 and identified 31 with gastrointestinal symptoms; none of the children developed autism [ 16]. A further analysis of this cohort revealed no vaccine-associated cases of autism among 1.8 million children [ 17]. Although this cohort was analyzed using a passive surveillance system, the complete absence of an association between gastrointestinal disease and autism after MMR vaccination was compelling.

Thimerosal

Thimerosal-50% ethylmercury by weight-is an antibacterial compound that has been used effectively in multidose vaccine preparations for >50 years [ 18] (thimerosal is not contained in live-virus vaccines, such as MMR). In 1997, the US Food and Drug Administration Modernization Act mandated identification and quantification of mercury in all food and drugs; 2 years later, the US Food and Drug Administration found that children might be receiving as much as 187.5 µg of mercury within the first 6 months of life. Despite the absence of data suggesting harm from quantities of ethylmercury contained in vaccines, in 1999, the American Academy of Pediatrics and the Public Health Service recommended the immediate removal of mercury from all vaccines given to young infants [ 19]. Widespread and predictable misinterpretation of this conservative, precautionary directive, coupled with a public already concerned by a proposed but unsubstantiated link between vaccination and autism, understandably provoked concern among parents, which led to the birth of several antimercury advocacy groups. However, because the signs and symptoms of autism are clearly distinct from those of mercury poisoning, concerns about mercury as a cause of autism were-similar to those with MMR vaccine-biologically implausible [ 20]; children with mercury poisoning show characteristic motor, speech, sensory, psychiatric, visual, and head circumference changes that are either fundamentally different from those of or absent in children with autism. Consistent with this, a study performed by scientists at the Centers for Disease Control and Prevention years later showed that mercury in vaccines did not cause even subtle signs or symptoms of mercury poisoning [ 21].

Despite the biological implausibility of the contention that thimerosal in vaccines caused autism, 7 studies-again descriptive or observational-were performed ( table 2). Four other studies have been reviewed in detail elsewhere [ 28] but are not discussed here because their methodology is incomplete and unclear and, thus, cause difficulty in drawing meaningful conclusions.

Ecological studies.Three ecological studies performed in 3 different countries compared the incidence of autism with thimerosal exposure from vaccines. In each case, the nationwide removal of thimerosal-which occurred in 1992 in Europe and in 2001 in the United States-allowed robust comparisons of vaccination with thimerosal-containing and thimerosal-free products, as follows:

1. In Sweden and Denmark, researchers found a relatively stable incidence of autism when thimerosal-containing vaccines were in use (1980-1990), including years when children were exposed to as much as 200 µg of ethylmercury (concentrations similar to peak US exposures) [22]. However, in 1990, a steady increase in the incidence of autism began in both countries and continued through the end of the study period in 2000, despite the removal of thimerosal from vaccines in 1992.

2. In Denmark, researchers performed a study comparing the incidence of autism in children who had received 200 µg (1961-1970), 125 µg (1970-1992), or 0 µg of thimerosal (1992-2000) and again demonstrated no relationship between thimerosal exposure and autism [23].

3. In Quebec, researchers grouped 27,749 children from 55 schools by date of birth and estimated thimerosal exposure on the basis of the corresponding Ministry of Health vaccine schedules. School records were obtained to determine age-specific rates of pervasive developmental disorder [9]. Thimerosal exposure and pervasive developmental disorder diagnosis were found to be independent variables. Similar to previous analyses, the highest rates of pervasive developmental disorder were found in cohorts exposed to thimerosal-free vaccines. The results were unchanged when both exposure and outcome definitions varied.

Cohort studies.Four cohort studies that examined thimerosal exposure and autism have been performed, as follows:

1. In Denmark, researchers examined >1200 children with autism that was identified during 1990-1996, which comprised ∼3 million person-years. They found that the risk of autism did not differ between children vaccinated with thimerosal-containing vaccines and those vaccinated with thimerosal-free vaccines or between children who received greater or lower quantities of thimerosal [24]. They also found that the rates of autism increased after the removal of thimerosal from all vaccines.

2. In the United States, using the Vaccine Safety Data Link, researchers at the Centers for Disease Control and Prevention examined 140,887 US children born during 1991-1999, including >200 children with autism [25]. The researchers found no relationship between receipt of thimerosal-containing vaccines and autism.

3. In England, researchers prospectively followed 12,810 children for whom they had complete vaccination records who were born during 1991-1992, and they found no relationship between early thimerosal exposure and deleterious neurological or psychological outcomes [26].

4. In the United Kingdom, researchers evaluated the vaccination records of 100,572 children born during 1988-1997, using the General Practice Research Database, 104 of whom were affected with autism [27]. No relationship between thimerosal exposure and autism diagnosis was observed.

Too Many Vaccines

When studies of MMR vaccine and thimerosal-containing vaccines failed to show an association with autism, alternative theories emerged. The most prominent theory suggests that the simultaneous administration of multiple vaccines overwhelms or weakens the immune system and creates an interaction with the nervous system that triggers autism in a susceptible host. This theory was recently popularized in the wake of a concession by the Vaccine Injury Compensation Program with regard to the case of a 9-year-old girl with a mitochondrial enzyme deficiency whose encephalopathy, which included features of autism spectrum disorder, was judged to have worsened following the receipt of multiple vaccines at age 19 months [29]. Despite reassurances by the Centers for Disease Control and Prevention that the Vaccine Injury Compensation Program's action should not be interpreted as scientific evidence that vaccines cause autism, many in the lay press and the public have not been reassured.

The notion that children might be receiving too many vaccines too soon and that these vaccines either overwhelm an immature immune system or generate a pathologic, autism-inducing autoimmune response is flawed for several reasons:

1. Vaccines do not overwhelm the immune system. Although the infant immune system is relatively naive, it is immediately capable of generating a vast array of protective responses; even conservative estimates predict the capacity to respond to thousands of vaccines simultaneously [ 30]. Consistent with this theoretical exercise, combinations of vaccines induce immune responses comparable to those given individually [ 31]. Also, although the number of recommended childhood vaccines has increased during the past 30 years, with advances in protein chemistry and recombinant DNA technology, the immunologic load has actually decreased. The 14 vaccines given today contain <200 bacterial and viral proteins or polysaccharides, compared with >3000 of these immunological components in the 7 vaccines administered in 1980 [ 30]. Further, vaccines represent a minute fraction of what a child's immune system routinely navigates; the average child is infected with 4-6 viruses per year [ 32]. The immune response elicited from the vast antigen exposure of unattenuated viral replication supersedes that of even multiple, simultaneous vaccines.

2. multiple vaccinations do not weaken the immune system. Vaccinated and unvaccinated children do not differ in their susceptibility to infections not prevented by vaccines [ 33, -, 35]. In other words, vaccination does not suppress the immune system in a clinically relevant manner. However, infections with some vaccine-preventable diseases predispose children to severe, invasive infections with other pathogens [ 36, 37]. Therefore, the available data suggest that vaccines do not weaken the immune system.

3. Autism is not an immune-mediated disease. Unlike autoimmune diseases such as multiple sclerosis, there is no evidence of immune activation or inflammatory lesions in the CNS of people with autism [ 38]. In fact, current data suggest that genetic variation in neuronal circuitry that affects synaptic development might in part account for autistic behavior [ 39]. Thus, speculation that an exaggerated or inappropriate immune response to vaccina-tion precipitates autism is at variance with current scientific data that address the pathogenesis of autism.

4. No studies have compared the incidence of autism in vaccinated, unvaccinated, or alternatively vaccinated children (i.e., schedules that spread out vaccines, avoid combination vaccines, or include only select vaccines). These studies would be difficult to perform because of the likely differences among these 3 groups in health care seeking behavior and the ethics of experimentally studying children who have not received vaccines.

Conclusions

Twenty epidemiologic studies have shown that neither thimerosal nor MMR vaccine causes autism. These studies have been performed in several countries by many different investigators who have employed a multitude of epidemiologic and statistical methods. The large size of the studied populations has afforded a level of statistical power sufficient to detect even rare associations. These studies, in concert with the biological implausibility that vaccines overwhelm a child's immune system, have effectively dismissed the notion that vaccines cause autism. Further studies on the cause or causes of autism should focus on more-promising leads.

Acknowledgments

Potential conflicts of interest.P.A.O. is a coinventor and patent coholder of the rotavirus vaccine Rotateq and has served on a scientific advisory board to Merck. J.S.G.: no conflicts.

References

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Vaccines and Autism: A Tale of Shifting Hypotheses | Clinical Infectious Diseases | Oxford Academic

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Although child vaccination rates remain high, some parental concern persists that vaccines might cause autism. Three specific hypotheses have been proposed: (1) the combination measles-mumps-rubella vaccine causes autism by damaging the intestinal lining, which allows the entrance of encephalopathic proteins; (2) thimerosal, an ethylmercury-containing preservative in some vaccines, is toxic to the central nervous system; and (3) the simultaneous administration of multiple vaccines overwhelms or weakens the immune system.

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Changes in Math

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Key Shifts in Mathematics | Common Core State Standards Initiative

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The Common Core State Standards for Mathematics build on the best of existing standards and reflect the skills and knowledge students will need to succeed in college, career, and life. Understanding how the standards differ from previous standards-and the necessary shifts they call for-is essential to implementing them.

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New evidence that vaccinations cause Autism. This effects people in my city and at my school close to me. This situation shows how knowledge of areas of knowing such as natural life sciences can change over time. The evidence that getting a child vaccinated can cause Autism is new knowledge and new theories. There hasn't always been the idea that vaccines lead to Autism, which is further evidence that as time goes on, our knowledge of certain subjects change and grow.

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Manuel Lima: A visual history of human knowledge

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How does knowledge grow? Sometimes it begins with one insight and grows into many branches; other times it grows as a complex and interconnected network. Infographics expert Manuel Lima explores the thousand-year history of mapping data -- from languages to dynasties -- using trees and networks of information.