Should thimerosal-containing vaccines be banned worldwide?

One of the oldest topics I’ve dealt with on this blog, a topic that I’ve been writing about on and off (unfortunately, mostly on) about the antivaccine movement. Ever since I first discovered about a decade ago that, yes, there are people ignorant enough about science and medicine that they actually think that vaccines are harmful and cause autism, as well as actually believing that it is a good idea not to vaccinate their children against even deadly diseases like the measles, polio, Haemophilus influenzae type B (HiB), and more. As a group, hiding behind the risible claim that they are “not antivaccine” but rather “pro-vaccine safety,” whether they admit it or not, they seem bound and determined to allow the return of diseases that had been brought under control or even, like polio, on the brink of being eliminated.

While overseas, particularly in the U.K., the vaccine bogeyman is the MMR vaccine, thanks to a campaign of fear stoked by a British gastroenterologist and incompetent scientist named Andrew Wakefield who was also in the pay of trial lawyers looking to sue vaccine manufacturers. In the U.S, the vaccine bogeyman is a preservative used to prevent bacterial contamination of multi-dose vials known as thimerosal. What makes thimerosal so easy to demonize is that it just so happens to contain mercury, and back in the 1990s the myth that mercury in thimerosal-containing vaccines (TCVs) causes autism spread throughout the U.S., even though there was no compelling evidence that TCVs were in any way correlated with the risk of autism or autism spectrum disorders. It is a hypothesis that had a tiny modicum of plausibility 15 years ago but whose plausibility has long been crushed. It is a failed hypothesis. Even though it was pretty well established that this was the case back in 1999, the FDA and CDC still moved to remove thimerosal from vaccines in 1999, a process that was complete by the end of 2001. Since then, it’s gone way beyond “pretty well established” and into the realm of a falsified hypothesis. The idea that mercury in vaccines is in any way related to autism is about as falsified as a hypothesis can be, particularly in light of multiple studies that have failed to find a decrease in the prevalence of autism in the years since 2001, something that should have happened by now if TCVs contributed to autism.

Even though the evidence shows that TCVs do not cause autism, thimerosal is not used in vaccines in the U.S. and developed countries. However, in the U.S. and developed countries, we can afford single-dose vials of vaccine that do not require a preservative, either thimerosal or another preservative to take its place. We also have ready access to refrigeration for these vaccines. Such is not necessarily the case in much of the world, particularly in impoverished Third World countries, where cost and access to adequate refrigeration are major considerations. Reflecting this reality, public health experts and doctors have warned about one perils of banning mercury in certain processes and products:

A group of prominent doctors and public health experts warns in articles to be published Monday in the journal Pediatrics that banning thimerosal, a mercury compound used as a preservative in vaccines, would devastate public health efforts in developing countries.

Representatives from governments around the world will meet in Geneva next month in a session convened by the United Nations Environmental Program to prepare a global treaty to reduce health hazards by banning certain products and processes that release mercury into the environment.

But a proposal that the ban include thimerosal, which has been used since the 1930s to prevent bacterial and fungal contamination in multidose vials of vaccines, has drawn strong criticism from pediatricians.

They say that the ethyl-mercury compound is critical for vaccine use in the developing world, where multidose vials are a mainstay.

Banning it would require switching to single-dose vials for vaccines, which would cost far more and require new networks of cold storage facilities and additional capacity for waste disposal, the authors of the articles said.

Perhaps the key article published online in Pediatrics is entitled Global Justice and the Proposed Ban on Thimerosal-Containing Vaccines by Katherine King, Megan Paterson and Shane K. Green. King et al begin the article by pointing out that thimerosal-free single dose vials of vaccines were introduced into high income countries as a “precautionary move, now known to be unfounded. However, for low- and middle income countries, where, the authors note, the burden of vaccine-preventable diseases are most severe, multi-dose vials of TCVs are a critical part of immunization programs. Indeed, the authors point out that switching away from TCVs in such countries would have a high price:

Extensive additional resources associated with increased manufacturing, shipping, cold-chain storage, administration, and waste-handling infrastructure would be required by a move away from multidose vaccines; for example, a shift to single-dose vials would increase the annual cost of Pan American Health Organization– or UNICEF–supplied vaccines by .$300 million.

In early 2013 governments will be set to finalize the products and processes that will be prohibited in a multilateral environmental treaty whose purpose is to limit human exposure to mercury. While I agree that this is a laudable goal, as do the authors of this commentary, such a move could have severe unintended consequences for global vaccination programs, which is why the World Health Organization and “much of the broader scientific and public health community” have recommended that thimerosal-containing vaccines be exempt from any ban on mercury-containing products, in order to avoid compromising global vaccination efforts in the very countries where strong vaccination programs are most needed.

One of the interesting aspects of those arguing against such an exemption is that they think it’s a matter of justice. In other words, they argue that it’s unjust to subject children in impoverished nations to a compound whose exposure is being limited in everyone else. I’ve heard this argument before. Basically, it involves the implication that we are somehow willing to “poison” poor people, that it’s somehow hypocritical to be willing to allow the use of a substance in poor countries that we do not use in our own. Superficially, it sounds like a compelling argument, but it rests on a false premise. That’s why to this the authors respond that difference does not necessarily signal injustice. I think I’ll let King et al explain, because the they do it well:

Although vaccines containing thimerosal are more widely used in LMICs than in HICs, a difference in immunization practice that would persist if thimerosal use were to continue in LMICs, the charge of injustice is misguided. Different practices, in and of themselves, do not make for injustice; they are morally problematic only if they are unjustified and compromise the interests of the affected parties. The moral intuition at work here is one of equality, that each life must be treated with equal respect and regard. Treating individuals with equal regard, however, does not mean that all people are treated the same in all respects. Indeed, promoting equality in 1 sphere, such as health, often requires that people be treated differently in response to their unique needs and circumstances. It is only when differences in practice are not justified by differences in the needs and circumstances of the target individual or group, leading to avoidable harms, that concerns of injustice and inequality arise. Thus, the use of thimerosal-containing vaccines in some jurisdictions but not others would only be unjust if this practice were harmful and unjustified. Neither is true.

King et al then go on to point out that there is “no credible scientific evidence” that TCVs represent any threat to human health, which is true. Like the parrot in the famous Monty Python sketch, the hypothesis that TCVs cause autism is, deader than dead can be. Antivaccinationists will tell you that it’s “pining for the fjords,” but in reality It’s not pinin,’ it’s passed on! This hypothesis is no more! It has ceased to be! It’s expired and gone to meet its maker! This is a late hypothesis! It’s a stiff! Bereft of life, it rests in peace! If antivaccinationists hadn’t nailed it to its perch it would be pushing up the daisies! Its metabolical processes are of interest only to historians! It’s hopped the twig! It’s shuffled off this mortal coil! It’s run down the curtain and joined the choir invisible! This…. is an EX-HYPOTHESIS!

Sorry, I couldn’t resist. Besides, it’s been a long time since I’ve done that; so I was due.

Because there is no credible evidence to support the hypothesis that TCVs do any of the harms attributed to them by antivaccinationists (or any harm at all other than occasional local reactions), King et al conclude:

In the absence of risk to human health, the use of thimerosal in vaccination programs in LMICs presents no threat of injustice. Rather, it is banning thimerosal that would cause an injustice to those living in LMICs and relying on these vaccines for effective protection against many harmful infectious diseases. Currently, multidose vaccines containing thimerosal are used in .120 countries to immunize ∼84 million children every year,19 saving the lives of ∼1.4 million people annually. 20 They are also used throughout the world, including the United States and other HICs, for pandemic influenza vaccines, because it allows for more rapid production and easier dissemination of the vaccines.20 And yet, banning thimerosal would amount to banning such multidose vaccines, including tetanus toxoid, diphtheriatetanus- whole cell pertussis, and hepatitis B vaccines.

The results would be potentially catastrophic. Leaving cost aside, while the infrastructure and manufacturing capabilities to replace multi-dose TCVs with single-dose preservative-free vials, there would be an enormous strain on the resources and public health infrastructure of low income countries. Even if the challenges could be met, disruption to vaccine supplies would be inevitable, and such supply disruptions would be likely to last for several years, which is why King et al pose a question:

Not surprisingly, during the course of negotiations, LMIC governments have questioned whether thimerosal should be exempted from the treaty.25 The resistance to its continued use comes entirely from nongovernmental organizations in HICs, the populations of which would not suffer the consequences of the potential ban. Where’s the justice in that?

Where indeed?

That is why the American Academy of Pediatrics has endorsed the recommendation of the WHO’s Strategic Advisory Group of Experts regarding TCVs, particularly given that there is no viable alternative to thimerosal that can be used as a preservative in multi-dose vaccine vials.

Predictably, the antivaccine loons have come out of the woodwork over this. For example, over at the MedPageToday report on the AAP’s recommendation, the commenters are overwhelmingly antivaccine loons ranting at big pharma, throwing down fallacies about thimerosal, and in general spewing the usual long-debunked and scientifically unsupported canards, along with a heapin’ helpin’ of pure paranoid conspiracy mongering. It’s truly depressing to behold; the reason-based community there could really use some tactical air support. And, of course, the merry band of antivaccine propagandists over at the antivaccine crank blog, Age of Autism, are enraged—enraged, I tell you!—at the AAP. (When are they ever not enraged at the AAP and CDC?)

Personally, I’d actually go further than the AAP and WHO here. I’d argue that the claimed link between TCVs and autism has been so thoroughly falsified that it would not be unreasonable to lift the ban on TCVs in all countries, not just impoverished countries. After all, even here in the U.S., we have areas with poor children who could benefit from less expensive, more available vaccines. It won’t happen, of course, but it’s not as crazy as antivaccinationists would make you think it sounds.