Here we go again.
Having been in the blogging biz for nearly seven years and developed a special interest in the anti-vaccine movement, I think I've been at this long enough to make some observations with at least a little authority. One thing that I've noticed is a very consistent pattern in which, every time a new study or report released that either fails to find evidence that vaccines cause autism or significant harm or that even concludes that vaccines do not cause autism, the anti-vaccine movement is right there, ready to attack it with pseudoscience, misinformation, and exaggerations of the study's or report's shortcomings. Indeed, outside of anthropogenic global warming (AGW) denialists, I can't think of another group of science or medicine denialists besides anti-vaccine loons who have such an efficient "rapid response team." Inevitably, any time a major study or report is released exonerating vaccines, it's a sure bet that within 24 hours one of the major anti-vaccine groups will have a press release ready or that wandering home of happy anti-vaccine sycophants, toadies, and lackies, Age of Autism, will have pseudoscience-laden pseudo-rebuttal.
This time around, it's a major report by the Institute of Medicine (IOM), entitled Adverse Effects of Vaccines: Evidence and Causality. This 667 page report is the result of a long effort by an IOM committee of 16 charged with examining the evidence linking adverse events with vaccines. The overall conclusion was--surprise! surprise!--that vaccines are safe. Before I dig into the results a bit more, here's how the report came about:
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 tetanus- containing vaccines that do not carry the whole-cell pertussis component.
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.
The VICP, as regular readers of this blog probably remember, is the Vaccine Injury Compensation Program. In this program, claims of vaccine injury are adjudicated in an expedited manner in a special court known as the Vaccine Court. The Autism Omnibus was decided through the VICP and the Vaccine Court over two years ago. As I've explained before as well, the Vaccine Court uses less rigorous scientific standards than normal courts, and there are certain injuries known as "table injuries" that are almost automatically assumed to be due to vaccines. In any case, I consider it important that the committee didn't even consider efficacy, because this provides an estimate of just the known risks. Doing this was somewhat risky, because risks discussed outside the context of the benefits of vaccines can give a distorted picture of the true risk-benefit ratio. On the other hand, by focusing like the proverbial cliched laser on just adverse events, the committee could provide an estimate of the true absolute risk of each adverse event.
Obviously, I haven't read the entire 667 page report. It was only released yesterday; I doubt even the anti-vaccine groups who are even now poring over each page looking for weaknesses to attack have read the entire report yet. However, the executive summary provides sufficient information for a "first pass" analysis of its findings, which assign each relationship (between a vaccine and a specific adverse event) to one of four categories:
- 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 methodology the committee used to assess the weight of evidence involved examining the weight of epidemiological evidence linking the adverse event to the specific vaccine in question, the weight of mechanistic evidence (one could view this criterion as asking, "Is there biological plausibility linking this particular adverse event with this particular vaccine?"), and the results of its causality assessment. How the committee went about its work, weighted each form of evidence, and came to its conclusions is summarized in this figure:
So, let's summarize the results of the report and what the committee concluded. First, here are the adverse events for which the committee concluded that the evidence convincingly supports a causal relationship, which were well-summarized in this article:
- Fever-triggered seizures, which seldom cause long-term consequences, from the measles-mumps-rubella, or MMR, vaccine.
- MMR also can cause a rare form of brain inflammation in some people with immune problems.
- The varicella vaccine against chickenpox sometimes triggers that viral infection, resulting in widespread chickenpox or a painful relative called shingles. It also occasionally can lead to pneumonia, hepatitis or meningitis.
- Six vaccines -- MMR and the chickenpox, hepatitis B, meningococcal and tetanus-containing vaccines -- can cause severe allergic reactions known as anaphylaxis.
- Vaccines in general sometimes trigger fainting or a type of shoulder inflammation.
The adverse reactions for which the existing evidence favors acceptance include HPV vaccine and anaphylaxis (severe allergic reaction), MMR vaccine and transient arthralgia (joint pain) in female adults, MMR vaccine and transient arthralgia in children, and certain trivalent influenza vaccines used in Canada and a mild and temporary oculorespiratory syndrome. One of these conclusions (the relationship between anaphylaxis and the HPV vaccine) was only based on mechanistic evidence.
More interestingly, what will likely result in great unhappiness among the anti-vaccine movement were the relations for which the evidence, according to the committee, favors rejection. These include claimed correlations between MMR vaccine and type 1 diabetes, DTaP vaccine and type 1 diabetes, MMR vaccine and autism, inactivated influenza vaccine and asthma exacerbation or reactive airway disease episodes, and inactivated influenza vaccine and Bell's palsy. Let me repeat that again: The evidence does not support the claim that the MMR vaccine causes autism, just as it doesn't support any relationship between vaccines and autism.
Finally, the committee concluded that for the vast majority of the proposed causal relationship pairs there isn't enough evidence to accept them or reject them. This shouldn't be construed to mean, however, that there is a high probability that vaccines cause these adverse reactions. The reasons that the committee concluded that there was "insufficient evidence" is because many of these particular adverse reactions were so uncommon that it is not possible to make a conclusion regarding whether or not the vaccine is causally associated. Indeed, listen to the chair of the committee, Dr. Ellen Wright Clayton:
Not surprisingly, the vast majority of their decisions -- 133 -- fell into the inadequate category, including many concerns associated with the HPV vaccine. But that doesn't mean that the data is simply inconclusive, says Clayton. In fact, that category is quite diverse, encompassing cases in which studies show both a potential connection or no connection between vaccines and an adverse event; it also includes cases in which the information simply doesn't exist -- yet --to make a sound scientific conclusion. That's the case with HPV, which hasn't been used long enough in enough people to generate robust data on many of the potential side effects, such as neurological conditions that have been linked to the vaccine in some.
In another article, Clayton points out: "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."
And so it is, although no doubt vaccine denialists won't see it that way.
It should also be noted that all of these complications, even the ones for which the committee considered the evidence to be such that it convincingly supported a causal relationship are very uncommon--rare, even. Indeed, as Dr. Clayton put it, "Despite looking very hard, it was really hard to find that vaccines cause injuries and the injuries they do cause are generally pretty mild and self-contained."
Which is pretty much what we've known all along.
Another thing that's important about this study is that it is strong evidence that, contrary to the claims of the anti-vaccine movement, adverse reactions to vaccines are not hidden; they are not swept under the rug. In fact, the government and the IOM have gone to great lengths to look for adverse events and to try to correlate them to specific vaccines. Before this report was ever conceived, real scientists and real doctors spent lots and lots of money and effort to study vaccines, autism, and whether there is a relationship between the two, even after the weight of the evidence strongly suggested that there is not. They've also studied virtually every adverse event you can imagine. Synthesizing the estimates of risk derived from the scientific literature from hundreds upon hundreds of papers, the committee concluded that adverse reactions are rare and that adverse reactions commonly claimed by the anti-vaccine movement (autism, type I diabetes) are not supported by the data.
In any rational, reasonable world, this report would be highly reassuring, and to most parents I hope it will be. I'm also under no illusions that it will persuade the anti-vaccine movement in any way. Indeed, the anti-vaccine group SafeMinds was the first off the mark with a press release (shilled for by, of course, the anti-vaccine propaganda blog Age of Autism. Naturally, SafeMinds tries to take the part of the report that concludes that insufficient evidence exists to confirm or deny a causal relationship between specific vaccines and specific adverse events and spin it to mean that the safety of vaccines is not known. Not surprisingly, there's the requisite conspiracy-mongering, where SafeMinds accuses the government of a conflict of interest by pointing out that:
The IOM report took two years to produce, mostly behind closed doors, and was paid for by the Department of Health and Human Services, the government agency which is also a defendant against the vaccine-injured in the government's vaccine court.
SafeMinds then provides yet another example of Orwellian spin:
The report investigated 158 potential adverse outcomes from vaccines. Of these, 135 or 85% were found to have inadequate research to accept or reject a causal association. Of the 23 outcomes where the research was deemed adequate, 18 or 78% were found supportive of harm. Vaccines were cleared of safety concerns for just five of the outcomes considered. "These statistics are hardly reassuring to parents who are now asked to give their young children over 32 vaccinations," noted Sallie Bernard, President of SafeMinds.
Predictably (at least, I predicted it), SafeMinds goes for raw numbers and tries to make it seem as though because there was inadequate evidence to accept or reject a causal relationship between these adverse events and vaccines that there is real uncertainty about the safety of vaccines. Of course, SafeMinds' flack fails to mention that the reason there is inadequate evidence is because these adverse reactions are so rare that there are just too few of them to make any definitive conclusions about causality with respect to vaccines. It would take enormous studies with huge numbers of subjects to have any hope of teasing out causality, and even then the events might be too rare to make any definitive conclusions.
All of this, to SafeMinds, is not surprisingly a call for "more research":
SafeMinds calls on Congress and the Administration to institute a rigorous science program on vaccine safety. This program would include the establishment of an independent Vaccine Safety Agency (similar to the National Transportation Safety Board), the launch of a study comparing health outcomes between vaccinated and unvaccinated children, the inclusion of vaccines as an exposure variable in the National Children's Study and mandatory reporting by physicians to the Vaccine Adverse Event Reporting System.
I've already explained why the whole "vaxed versus unvaxed" study is highly unlikely to be particularly informative. Basically, SafeMinds is spinning the report into one massive appeal to ignorance, arguing that, if we don't have adequate evidence to make a conclusion regarding whether vaccines cause these very rare events, then vaccines must not be safe and we have to "do more research." It's a highly predictable response, given the history of the anti-vaccine movement in doing exactly the same thing with previous studies. No matter how much research fails to find evidence of a link between vaccines and autism, anti-vaccinationists call for "more research." When the MMR vaccine and then later thimerosal in vaccines were exonerated as causes of autism, the anti-vaccine movement turned almost on a dime and started blaming other ingredients (the "toxins gambit," a favorite distortion also sometimes known as "Green Our Vaccines") and the vaccine schedule as a whole (the "too many too soon" gambit), neither of which has good scientific evidence to support it. The implication of these latest tactics ends up being a call for testing, in essence, each vaccine ingredient and combination of vaccines independently, which is logistically incredibly expensive to the point of being virtually impossible) and doing their holy grail of a study, the "vaxed versus unvaxed" study, which, because it would be utterly unethical to do as a randomized clinical trial or even as a prospective study, would have to be retrospective and thus prone to the typical confounding factors all retrospective studies are prone to.
The IOM report is yet another indication that serious vaccine reactions are rare and that in general most adverse reactions to vaccines are mild in nature. That is not to say that they are nonexistent, but they are much less frequent and much less severe than the impression that is intentionally promoted by anti-vaccine activists. These conclusions should reassure most people who are willing to listen, but groups like SafeMinds are anything but willing to listen. The bottom line is that anti-vaccine beliefs are not based on evidence or data, no matter how much anti-vaccine believers try to distort scientific data or do bad science themselves (like Mark and David Geier or Andrew Wakefield) to represent their fear and loathing of vaccines as being "evidence-based." No matter how many scientific studies, systematic reviews of the literature, meta-analyses, and other evidence exonerate individual vaccines or vaccines as a whole as a cause for autism and the other conditions, the anti-vaccine movement will not be swayed. Because to groups like SafeMinds, Generation Rescue, the National Vaccine Information Center, and others, it's first and foremost about the vaccines. It's always about the vaccines. It always will be about the vaccines.