Antivaxxers spread misinformation. This does not have to be the case – I can envision those who wish to function as watchdogs on the vaccine industry or prioritize personal freedom over government programs (even good ones), but who strive to be logical and evidence-based. The culture within the anti-vaccine movement, however, is not logical and evidence-based. Rather, they spread whatever misinformation supports their rather extreme ideology – that vaccines do not work and are dangerous.

Countering anti-vaccine misinformation can be almost a full time job. It is the proverbial game of whack-a-mole, especially in the social media age where old debunked anti-vaccine memes can resurface over and over again on Facebook or Twitter. The game is also rigged in that it is easier to spread fear with misinformation than to reassure with accurate information. Even if we address every anti-vaccine trope, parts of the public can be left with the vague sense that there is something dangerous about vaccines, or that the government is not playing entirely straight with us.

In any case, here is this week’s edition of whack the anti-vaccine mole. The particular varmint that popped its head up recently is the claim that 2-5% of children who receive the MMR vaccine (mumps-measles-rubella trivalent vaccine) contract measles from the vaccine. This specific claim was made on the realfoodeater blog (another thing you should know about the anti-vaccine community is the broad overlap with the natural, alternative medicine, and conspiracy subcultures). The blogger gave as a reference a conversation she had with an unnamed doctor at DeVos Children’s Hospital.

This, of course, is a huge problem with medical information on social media – much of it is second-hand information passed through non-experts, often through thick ideological filters. Can there be any truth to this particular claim?

The measles component of the MMR vaccine is a live attenuated virus. Some vaccines use only parts of organisms, some used whole killed organisms, and some use live attenuated viruses. A live virus vaccine does cause an actual infection, just a weakened one that the immune system should have no problem fighting off, resulting in lasting immunity without having to suffer from the full-blown illness.

Viruses are attenuated for such vaccines by culturing them in a non-human medium, in this case, chicken embryos. The virus essentially adapts to the non-human host and over time loses its adaptations to humans and so becomes less virulent. In the case of the attenuated measles virus, it replicates much more slowly in human hosts, giving the immune system time to gear up and wipe it out before it can cause any serious problems.

Where the 2-5% figure likely comes from is that this percentage of children who receive the MMR vaccine will get a mild measles-like rash. This is not full-blow measles, however. It is easy to see how the blogger could have misunderstood this kind of information.

In order for the vaccine to cause an actual measles infection the attenuated virus would need to mutate back to its wild type, regaining some of its lost virulence. This can theoretically happen, but is extremely rare.

The meme that kids get measles from the vaccine goes beyond this one blogger. An anti-vaccine chiropractor, Tim O’Shea, makes this claim overtly. He has two references to support his claim – neither of which have anything to do with contracting measles from the vaccine. They report measles outbreaks among high school and secondary school children.

The reports, in fact, demonstrate that the MMR vaccine is mostly effective. These particular outbreaks spread through children who did not have antibodies to the measles virus. In the second report, for example, 99% of the students had been vaccinated, but 4.1% did not seroconvert (in line with other published data on antibody rates in those vaccinated). The outbreak spread only to those without antibodies.

Without the high vaccination rate of this population, the small outbreak could have become a major epidemic. It is entirely unclear how O’Shea concludes from these studies that either vaccines cause measles or that the vaccine does not work. He writes:

Before 1978, measles was a minor, self-limiting, immune-building disease of childhood. You wanted your child to get it because they would have lifetime immunity. Then in 1978, the MMR shot suddenly became part of the vaccine package for all kids. 3 doses. Even though the incidence was down by 90% by then.
After a decade or so, many incidents like the 2 cited above began occurring all over the country – groups of kids who obviously got measles from the shot itself. They got the exact disease the shot was pretending to prevent. Such examples continue to the present.

He does not explain how children contracted measles from a vaccine they received over a decade earlier. Here we also see other anti-vaccine memes – that the diseases vaccines prevent are not so bad, and that they were on their way out anyway, and the vaccines just made things worse. This is abject science denial.

This meme is epitomized in the book Melanie’s Marvelous Measles, claiming that it is good for children to contract these diseases as it builds “natural” immunity. I’m still waiting for the sequels – Peter’s Powerful Polio, and Tina’s Terrific Tetanus.

The World Health Organization, however, spells out the real toll of measles:

  • Measles is one of the leading causes of death among young children even though a safe and cost-effective vaccine is available.
  • In 2012, there were 122 000 measles deaths globally – about 330 deaths every day or 14 deaths every hour.
  • Measles vaccination resulted in a 78% drop in measles deaths between 2000 and 2012 worldwide.

Measles is also a significant cause of blindness in developing countries. This is not a benign disease.

The notion that measles builds the immune system is also misleading. The immune system develops perfectly well without this particular infection. Infection results in immunity to measles alone. Of course, vaccination results in immunity to measles with far less risk.


Anti-vaccine sources make demonstrably incorrect claims about diseases and vaccines. This is not a matter of opinion – they are doing it wrong.

The examples above are just the tip of the iceberg. They get the science wrong by making factual errors and misinterpreting the evidence. Further, when their mistakes are pointed out to them, they rarely make corrections. They continue to use the discredited arguments.

This is the pattern of behavior of an ideological group engaging in motivated reasoning. Some of them, however, have computers and spread their misinformation like a virus.

I guess that makes SBM a vaccine in that analogy. Now we just have to figure out how to increase compliance.

Addendum: I had asked the CDC if there were any reported cases of full measles (not just mild symptoms) from the MMR vaccine and this is their response:

We are aware of 3 reported potential cases of measles contracted from the MMR vaccine. These 3 cases are from published reports in persons with immune deficiencies which described measles inclusion body encephalitis after measles vaccination, documented by intranuclear inclusions corresponding to measles virus or the isolation of measles virus from the brain among vaccinated persons.  The time from vaccination to development of measles inclusion body encephalitis for these cases was 4–9 months, consistent with development of measles inclusion body encephalitis after infection with wild measles virus. In one case, the measles vaccine strain was identified.

Three total cases, and only one in which the measles vaccine strain was identified. This is out of millions of doses given. This is rare indeed.


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.