We have been writing about the measles and the measles vaccine a lot recently, because we are not only in the middle of an outbreak, we are in the middle of a global resurgence of measles. We are also in the middle of a heating up of the social media battle between antivaxxers and respectable scientists, health care providers, and science communicators.

Antivaxxers generally spread fear and misinformation in order to fight for their alleged right to spread disease and put others at risk. Yes – that is very one-sided framing, but it is appropriate, avoiding the trap of false equivalency. The antivaxxers are simply wrong, and their position is based largely on lies.

A reliable way to tell that one side of a debate lacks intellectual honesty is that they continue to spread the same misinformation after they have been corrected. Scientists debate, but when one side presents evidence to support their position, the other side must account for it. If the information is valid and rigorous, then the only intellectually honest thing to do is to change your position. This does not necessarily mean completely flipping to the other school of thought, but at the very least the debate must evolve when legitimate points are made and new evidence is brought to bear.

However, debates with pseudoscientists or science deniers do not evolve that way. The deniers raise the same points over and over, regardless of how many times they are thoroughly debunked. This puts us in the position of swatting down the same false claims over and over, but it must be done to keep the misinformation at bay.

The shedding myth

One antivaccine myth that raises its head every time there is an outbreak or the debate over vaccines heats up is the notion of vaccine shedding as a cause of disease spread. Shedding is a real phenomenon, and refers to a period of time during a viral infection when the virus is coming off the infected person in some way and is capable of infecting other people. The measles virus, for example, is very contagious. It sheds through the upper respiratory system in coughs and sneezes and will infect 90% of unprotected people who come into contact with the infected person.

The measles vaccine is a live attenuated virus vaccine, meaning that it contains a live measles virus that has been treated to be weakened so that it is not capable of causing an infection, but will still reproduce enough to cause an immune reaction, and therefore build up immunity to measles. But this has also enabled antivaxxers to argue that the live virus in the vaccine can cause illness, and even cause measles infection, and perhaps is responsible for measles outbreaks. They have no evidence to support this claim, but they make the insinuation by cherry picking isolated cases.

For example, antivaccine quack Dr. Suzanne Humphries (she is a homeopath, so she clearly embraces pseudoscience) in an article dated today, concludes:

Some of these cases are confirmed to be among those who have received the MMR vaccine, and for those who have not been vaccinated, is it possible they were infected from those recently vaccinated when the vaccine was still “shedding,” and that the vaccine-strain of measles was passed on from the vaccinated child to the unvaccinated child?

Beware of provocative claims that end in a question mark. That is basically saying that they can’t really prove their claim, but want to put it out there to generate fear and mistrust. Humphries and other antivaxxers are now obsessing over a case in British Columbia reported in 2013 of a two-year old who contracted measles in the middle of an outbreak and the strain matched the vaccine strain of the virus. It is still not clear if her infection was caused by the vaccine, but that is a probable interpretation. Even if we take that as a given – this is an isolated case, making such cases extremely rare.

Also – getting the illness from a live attenuated vaccine is not the same as shedding, and does not prove that shedding occurs. Here is what the evidence actually shows. There is some evidence that small amounts of the attenuated virus occurs in the lungs and nose after getting the MMR vaccine. However, this is still the attenuated virus, and so is too weak to cause infection. In addition, the amounts are too small to be contagious – they cannot spread to someone else.

Further, when directly studied in monkeys, the Schwarz strain of measles used in the vaccine was found to have no detectable shedding at all. And further still, another study in people found that those who have the virus but are asymptomatic (like after being vaccinated) found no evidence of shedding.

Humphries and others also point to studies showing measles RNA fragments in the urine of children who received the MMR vaccine. But this is not shedding – RNA fragments are not whole viruses, and are not capable of causing infection (which doesn’t spread through the urine anyway). The presence of viral RNA in the urine just means the vaccine is doing its job.

So every link in the claim that the MMR vaccine can cause a vaccine outbreak is wrong – there is little evidence for viral shedding after the vaccine, what little shedding may occur is of a weakened virus, and is not capable of spreading. The evidence strongly shows, therefore, that the MMR cannot cause a measles outbreak, and never has.

Further still – we know the causes of measles outbreaks. This is not a mystery to be solved. In the US measles outbreaks generally occur in undervaccinated or unvaccinated populations where one member brought a measles infection to the community through travel. The outbreak spread through the unvaccinated, or those who failed to develop immunity, or their immunity has waned. The latter is a minority – the vast majority are unvaccinated. So measles outbreaks are caused by antivaccine propaganda and fearmongering, not the MMR vaccine. The evidence is overwhelming and clear.

The battle continues

We are perhaps entering a new phase of the struggle to educate the public about the safety and efficacy of vaccines, in the face of growing antivaccine propaganda. After the Disney measles outbreak there was pushback against the antivaxxers, leading to some improved vaccine laws, but now the antivaxxers are pushing back themselves.

There are a couple of new wrinkles. The first are reports that some “internet savvy teens” who are unvaccinated because their parents are antivaxers, who are looking up the information for themselves and seeking vaccinations, against their parents’ wishes. This is potent story-telling, but it’s not clear how big a phenomenon this is. It does highlight the importance of taking this information struggle to social media – because regardless of regulations, people are doing their own “research” and deciding for themselves. As we have pointed out many times before – you cannot make an informed decision based on misinformation. So the health care community is obligated to correct misinformation and propaganda about vaccines, and other health issues for that matter. They need to engage on social media.

However, antivaxxers are not the only players in this game who lack intellectual integrity. There is now evidence that Russian social media disinformation campaigns are not only targeting politicians, they are spreading antivaccine views. It seems that their goal is to amplify discord in American society, and they have identified the anti-vaccine movement as a suitable target. This also fits their propaganda, as the anti-vaccine movement is built largely upon anti-government and anti-corporate (i.e. capitalism) conspiracy theories. They can sow strife and anti-government sentiment in one stroke.

By itself this does not mean that any claims of the anti-vaccine movement are wrong. The Russians might choose to amplify legitimate criticism of the government (although I haven’t seen this). It is true, however, as has been amply demonstrated in countless articles here and elsewhere, that the anti-vaccine movement is based upon false and misleading claims that have been debunked over and over. It is interesting that Russian trolls have hit upon them as a fertile target for spreading conflict through misinformation.

In any case this just means that the struggle for the hearts and minds of the American public through social media is now all the more complex. There are many bad actors in this space – charlatans, conspiracy theorists, quacks, con artists, snake-oil peddlers, and now Russian trolls. There are also well-meaning but misguided parents who are simply overwhelmed by the flood of misinformation and crafted deception. Unfortunately the social media model is such that the deceived become deceivers, and the cycle continues.

All the more reason for experts with a genuine interest in public health to stay involved.



Posted by Steven Novella