Monday, 29th of August 2011 Print



New York Times, August 25, 2011

Yet another panel of scientists has found no evidence that a popular vaccine causes autism. But despite the scientists’ best efforts, their report is unlikely to have any impact on the frustrating debate about the safety of these crucial medicines.

“The M.M.R. vaccine doesn’t cause autism, and the evidence is overwhelming that it doesn’t,” Dr. Ellen Wright Clayton, the chairwoman of the panel, assembled by the Institute of Medicine, said in an interview. She was referring to a combination against measles, mumps and rubella that has long been a focus of concern from some parents’ groups.

The panel did conclude, however, that there are risks to getting the chickenpox vaccine that can arise years after vaccination. People who have had the vaccine can develop pneumonia, meningitis or hepatitis years later if the virus used in the vaccine reawakens because an unrelated health problem, like cancer, has compromised their immune systems.

The same problems are far more likely in patients who are infected naturally at some point in their lives with chickenpox, since varicella zoster, the virus that causes chickenpox, can live dormant in nerve cells for decades. Shingles, a painful eruption of skin blisters that usually affects the aged, is generally caused by this Lazarus-like ability of varicella zoster.

The government had asked the institute to review the known risks of vaccines to help guide decisions about compensation for those who claim to have been injured by vaccines. Legislation passed by Congress in 1986 largely absolved vaccine makers of the risks of being sued for vaccine injuries and forced those who suffer injury to petition the government for compensation.

The government generally restricts compensation to cases involving children who suffer injuries that scientists deem to have been plausibly caused by vaccination, including seizures, inflammation, fainting, allergic reactions and temporary joint pain. But battles have raged for years over whether to expand this list, with most of the fighting revolving around autism.

Many children injured by vaccination have an immune or metabolic problem that is simply made apparent by vaccines. “In some metabolically vulnerable children, receiving vaccines may be the largely nonspecific ‘last straw’ that leads these children to reveal their underlying” problems, the report stated.

For instance, recent studies have found that many of the children who suffered seizures and lifelong problems after receiving the whole-cell pertussis vaccine, which is no longer used but once routinely caused fevers in children, actually had Dravet syndrome, a severe form of epilepsy. The flood of lawsuits over the effects of the whole-cell pertussis vaccine was the reason Congress created the national vaccine injury compensation program in the first place, and children who suffered seizures after getting this vaccine have been among the most well-compensated.

In retrospect, the whole-cell pertussis vaccine may have played little role in the underlying illness in many of these children other than to serve as its first trigger.

The Institute of Medicine is the nation’s most esteemed and authoritative adviser on issues of health and medicine, and its reports can transform medical thinking around the world. The government has asked the medicine institute to assess the safety of vaccines a dozen times in the past 25 years, hoping the institute’s reputation would put to rest the concerns of some parents that vaccines cause a host of problems, including autism. It has not worked.

Sallie Bernard, president of SafeMinds, a group that contends there is a link between vaccines and autism, said the latest report from the Institute of Medicine excluded important research and found in many cases that not enough research had been done to answer important questions.

“I think this report says that the science is inadequate, and yet we’re giving more and more vaccines to our kids, and we really don’t know what their safety profile is,” Ms. Bernard said. “I think that’s alarming.”

Dr. Clayton said: “We looked at more than a thousand peer-reviewed articles, and we didn’t see many adverse effects caused by vaccines. That’s pretty remarkable.”

A version of this article appeared in print on August 26, 2011, on page A19 of the New York edition with the headline: Vaccine Cleared Again as Autism Culprit.


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2)     Institute of Medicine Report, ‘Adverse Effects of Vaccine’

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Report Brief



Adverse Effects of Vaccines: Evidence and Causality

Immunizations are a cornerstone of the nation’s efforts to protect people from a host of infectious diseases. As required by the Food and Drug Administration, vaccines are tested for safety before they enter the market, and their performance is continually evaluated to identify any risks that might appear over time.

Vaccines are not free from side effects, or “adverse effects,” but most are very rare or very mild. Importantly, some adverse health problems following a vaccine may be due to coincidence and are not caused by the vaccine. As part of the evaluation of vaccines over time, researchers assess evidence to determine if adverse events following vaccination are causally linked to a specific vaccine, and if so, they are referred to as adverse effects. Under the National Childhood Vaccine Injury Act of 1986, Congress established the National Vaccine Injury Compensation Program (VICP) to provide compensation to people injured by vaccines. Anyone who thinks they or a family member—often a child—has been injured can file a claim.

The Health Resources and Services Administration (HRSA), the agency within the Department of Health and Human Services that administers VICP, can use evidence that demonstrates a causal link between an adverse event and a vaccine to streamline the claim process. As such, HRSA asked the Institute of Medicine (IOM) to review a list of adverse events associated with vaccines covered by VICP and to evaluate the scientific evidence about the event—vaccine relationship. The vaccines covered by VICP include all vaccines recommended by the Centers for Disease Control and Prevention (CDC) for routine administration in children. Adults who experience an adverse event following one of these childhood vaccines also are covered by the program. HRSA asked the IOM to review 8 of the 12 covered vaccines. These eight are the varicella zoster vaccine (used against chickenpox); the influenza vaccines(except for the H1N1 influenza vaccine distributed in 2009); the hepatitis B vaccine; the human papillomavirus(HPV) vaccine; the measles, mumps, and rubella (MMR) vaccine; the hepatitis A vaccine; the meningococcal vaccines, and tetanuscontaining vaccines that do not carry the wholecell pertussis component.

Examining the Evidence

The adverse events selected by HRSA for IOM review are ones for which people have submitted claims—successful or not—to VICP. The committee appointed to this study was not asked to assess the benefits or effectiveness of vaccines but only the risk of specific adverse events. Its conclusions reflect the best evidence available at the time. Some of the adverse events the committee examined already are accepted in the medical community, but they are minor or manageable—for example, a sudden allergic reaction called anaphylaxis that can follow the administration of some vaccines.

In its report, the committee explains its process for evaluating the list of adverse events and provides a set of 158 causality conclusions. The committee examined two types of evidence: epidemiologic evidence, which derives from studies of populations, and mechanistic evidence, which draws from biological and clinical studies. The committee evaluated each scientific article for its strengths and weaknesses and then assigned a “weight of evidence” ranking to both the epidemiologic and mechanistic bodies of studies.

The committee considered the weights of evidence and then reached a conclusion about the causal relationship between each vaccine and adverse health problem pairing. The committee began from a position of neutrality, presuming neither causation nor lack of causation, and moved from that position only when the combination of evidence suggested a more definitive assessment regarding causation. The figure provides an explanation of how the evidence influenced the causality conclusions.

Based on the totality of the evidence, the committee assigned each relationship to one of four categories of causation in which the evidence:

  • convincingly supports a causal relationship;
  • favors acceptance of a causal relationship;
  • favors rejection of a causal relationship; or
  • is inadequate to accept or reject a causal relationship.

The committee did not use a category to designate evidence that convincingly supports no causal relationship, because it is virtually impossible to prove the absence of a very rare relationship with the same certainty that is possible to establish the presence of one.


Evidence Convincingly Supports a Causal Relationship

The committee concludes that the evidence convincingly supports a causal relationship between some vaccines and some adverse events.

As a live vaccine, the varicella zoster vaccine is linked to four specific adverse events, all due to infection from the vaccine virus strain:

  • Disseminated varicella infection (widespread chickenpox rash shortly after vaccination)
  • Disseminated varicella infection with subsequent infection resulting in pneumonia, meningitis, or hepatitis in individuals with demonstrated immunodeficiencies
  • Vaccine strain viral reactivation (appearance of chickenpox rash months to years after vaccination)
  • Vaccine strain viral reactivation with subsequent infection resulting in meningitis or encephalitis (inflammation of the brain)

The MMR vaccine is linked to a disease called measles inclusion body encephalitis, which in very rare cases can affect people whose immune systems are compromised and usually occurs within a year of acute measles infection or vaccination. The MMR vaccine also is linked to febrile seizures, which are a type of seizure that occurs in infants and young children in association with fever. Febrile seizures are generally benign and hold no long-term consequences.

Six types of vaccines—MMR, varicella zoster, influenza, hepatitis B, meningococcal, and tetanuscontaining vaccines—are linked to anaphylaxis.

The committee also found convincing evidence of a causal relationship between injection of vaccine, independent of the antigen involved, and two types of adverse events, including syncope, or fainting, and deltoid bursitis, or frozen shoulder, characterized by shoulder pain and loss of motion.

Evidence Favors Acceptance of a Causal Relationship

The evidence favors acceptance of four vaccine–adverse event relationships. In these cases, the evidence is strong and generally suggestive, but not firm enough to be described as convincing. These relationships include:

  • HPV vaccine and anaphylaxis;
  • MMR vaccine and transient arthralgia (temporary joint pain) in female adults;
  • MMR vaccine and transient arthralgia in children; and
  • certain trivalent inactivated influenza vaccines used in Canada in some recent years and a mild and temporary oculorespiratory syndrome, which is characterized by conjunctivitis, facial swelling, and upper respiratory symptoms, including coughing and wheezing.

Evidence Favors Rejection of a Causal Relationship

The evidence favors rejection of five vaccine–adverse event relationships:

  • MMR vaccine and autism
  • MMR vaccine and type 1 diabetes
  • DTaP (tetanus) vaccine and type 1 diabetes
  • Inactivated influenza vaccine and Bell’s palsy (weakness of the facial nerve)
  • Inactivated influenza vaccine and exacerbation of asthma or reactive airway disease episodes in children and adults

Evidence Inadequate to Accept or Reject a Causal Relationship

For the vast majority, (135 vaccine-adverse event pairs), the evidence is inadequate to accept or reject a causal relationship. In many cases, the adverse event being examined is an extremely rare condition, making it hard to study. In these cases, there was not adequate evidence to determine if the vaccine was or was not causally associated.


As some of the conclusions suggest, individuals with certain characteristics are more likely to suffer certain adverse effects from particular immunizations. Individuals who have serious immunodeficiencies are clearly at increased risk for specific adverse reactions to live viral vaccines, such as MMR and varicella vaccines. Thus, the committee was able at times to reach more limited conclusions for subgroups of the population.


In applying consistent standards across all the evidence, the committee found that some conclusions were easy to reach: the evidence was clear and consistent or, in the extreme, completely absent. Others required substantial discussion and debate.

The committee was not charged with making recommendations, and it did not pinpoint any particular areas for continued research. Much research already occurs to determine the safety of vaccines for the populations for whom they are recommended. However, there is much to learn about the human immune system, autoimmunity, and the effects of genetic variation, all of which may influence how people respond to vaccines.

Vaccines offer the promise of protection against a variety of infectious diseases. Despite much media attention and strong opinions from many quarters, vaccines remain one of the greatest tools in the public health arsenal. Certainly, some vaccines result in adverse effects that must be acknowledged. But the latest evidence shows that few adverse effects are caused by the vaccines reviewed in this report.

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