From CNN:

In some recent years, there have been fewer than 100 cases nationwide. But the [measles] virus has made a comeback in other years, including 2019 -- largely due to anti-vaxers, experts say.

The article doesn't include any statements by any "experts" mentioning anti-vaxers.

Is the comeback of the measles virus "largely due to anti-vaxers?" Have other sources made a similar attribution?

Why don't I believe CNN? Its claim makes sense, right? Well, the Oxford Vaccine Group at the University of Oxford wrote (emphasis added):

People who oppose vaccination – the so-called “anti-vaxxers” – are often thought to be the reason for low vaccination rates. The truth is, anti-vaxxers don’t wholly explain low vaccination rates. The influence of the movement is often exaggerated and does not properly explain a complex situation.

So, is CNN's claim an exaggeration? Or is it the reality?

To clarify (as @redleo95 suggested): The accepted answer has to include data on anti-vaxxers.

To clarify (as @Fizz suggested): It is preferred if the accepted answer focuses on the US (and specifically, the 2019 measles outbreak).

Who are anti-vaxxers? (suggested by @redleo95 and only partially addressed in comments): Consider 1) "people/groups who possess an anti-vaccine sentiment" and/or 2) "people/groups who possess and actively advocate an anti-vaccine sentiment."

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    Very few reputable sources even suggest anything else ... – fredsbend Apr 21 at 3:26
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    Coincidentally, I just heard a claim from Andrew Wakefield of all people, in person if you'll believe it, that the comeback is due to measles being unique in its mutations. In other words, he suggests that the vaccination is setting us up for serious pandemic. Considering the source, take it with a grain of salt. – fredsbend Apr 21 at 3:32
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    @fredsbend Interesting! I will still look into measles and its mutations, won't hurt. – Barry Harrison Apr 21 at 3:33
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    @fredsbend curious. I've heard that influenza mutates like crazy - which is why you need a new vaccine each year and it's still a crapshoot - but I've never heard such of measles. OTOH, I've heard that measles were pretty much non-existent before the anti-vaccination craze. – John Dvorak Apr 21 at 8:55
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    The question could be improved by giving a proper definition or more explanation of what you consider to be "anti-vaxxers". – redleo85 Apr 21 at 17:03

The answer depends a lot on what mechanism you imply and who you consider to be "anti-vaxxers". If you consider anti-vaxxers to be all groups of people who as a group oppose vaccination (e.g. for political, religious or other reasons), then CNN is largely right.

If you are looking for a causal link between the anti-vaccination movement and the increasing number of measles cases, it will be hard to prove. Mainly, because no data is collected on why people who get infected did not get vaccinated beforehand. It's also hard to know the number of people who don't get vaccinated because of this movement (people may not get vaccinated for a variety of reasons).

However, the Center for Disease Control (CDC) publishes yearly figures on measles cases in the United States. These are the figures from 2010-2019. The CDC also published information to some of the outbreaks. There are three years with exceptionally high numbers of cases: 2014, 2018 and 2019. In 2014 and 2018 the majority of measles cases occurred in a small number of outbreaks in pockets of largely unvaccinated communities. 2014: 383 cases in the unvaccinated Amish Community, 2018: most of cases in the Jewish-orthodox community in NY State, NYC and New Jersey. For 2019, no specific reason has yet been given. One of the newest studies dealing with vaccine hesitancy and measles Papachrisanthou et al. conclude:

VPDs are on the rise in the US and worldwide secondary to parental misconceptions, vaccine hesitancy, waning immunity, and negative effects on herd immunity.

Olive et al. find that NMEs (non-medical exemptions) for children are on the rise in 12 of 18 states, who permit these exemptions.NMEs in 18 states from 2009 - 2017.

Marti et al. look for global reasons for vaccine hesitancy and find that:

The most frequently cited reasons for vaccine hesitancy globally related to (1) the risk-benefit of vaccines, (2) knowledge and awareness issues, (3) religious, cultural, gender or socio-economic factors.

An overview of the reasons can be seen in this graphic Frequency of main themes indicated as top three reasons for vaccine hesitancy within all WHO regions.

So the one of the main criticisms of the anti-vaxxer movement (risk of vaccines) is the biggest driver of vaccine hesitancy globally.

This influences the US, because international travelers carrying the virus come to the US and infect people in regions where the vaccination rate is low (Papachrisanthou et al.).

The majority of the 2018 measles outbreaks have been in unvaccinated individuals exposed to international travelers. Europe is also experiencing the highest measles outbreak in over 2 decades secondary to suboptimal vaccination rates.

As for expert opinion on a link between anti-vaccination and measles outbreaks: The WHO clearly states in this report,

Because of low coverage nationally, or pockets of low coverage, multiple WHO regions have been hit with large measles and diphtheria outbreaks causing many deaths.

Furthermore, the WHO has included vaccine hesitancy as one of the 10 threats to global health in 2019.

So CNN's claim is not an exaggeration. It depends, though, on who you consider to be "anti-vaxxers". If you include people who do not vaccinate for religious reasons in the anti-vaxxers, CNN is right. If you only include people who do not vaccinate because they believe conspiracy theories that vaccines are harmful to be anti-vaxxers, their influence is plausible, but it is difficult to prove causation.

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    Then it would probably help if you specified your answers and your interpretation of the CNN quote you mention. Especially you should specify who you include in "anti-vaxxers" and what kind of mechanism exactly you interpret "largely due to" to mean. As I wrote in the first paragraph, an answer might be impossible. – redleo85 Apr 21 at 16:45
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    But the number of people who do not vaccinate for religious reasons has remained fairly constant (and small) for a long time. The increase in unvaccinated people has been almost entirely due to anti-vax conspiracy theorists, and it is the increase that has caused the measles outbreaks. So it entirely reasonable to state the the outbreak is due to conspiracy-theory anti-vaxxers, even though there are also religious anti-vaxxers in the mix. – DJClayworth Apr 22 at 1:00
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    I am very hesitant to accept this question for reasons in the comments: (1) a bit too much speculation with a bit too definitive conclusion (there's only 1 source of numeric data!! That's way too few datapoints. More sources please?), (2) doesn't address the 2019 case, (3) doesn't really contain "expert opinion" (WHO link doesn't mention apprehension of vaccination or other anti-vaxx stuff. So, community: Should I accept this answer? Before posting any of my questions, I do some "background search." In this case, the answer hasn't taught me anything my background search didn't. – Barry Harrison Apr 22 at 21:50
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    @BarryHarrison The WHO document doesn't look like it's a peer reviewed publication. In important questions of public health I don't think answers that don't cite peer-reviewed publications should be "accepted answers" on skeptics.SE. – Christian Apr 25 at 11:29
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    @redleo85 : As the skeptic community I think we should uphold certain epistemic standards. We should especially uphold those standards when interfacing with a community like that of antivaxxers. The question of why we have a comeback of measles is an important question of public healthy whose studies is worthy of grants that fund it and we should be open about the absence of serious scientific investigation of that claim if there's in fact such an absence. – Christian Apr 26 at 12:15

This answer only covers the second question:

Have other sources made a similar attribution?

The Dean for the National School of Tropical Medicine at Baylor has said on twitter (emphasis added):

More bad news...a totally unnecessary and self inflicted wound, and a direct consequence of an aggressive #antivax misinformation campaign

The New York City Health Commissioner has said

This outbreak is being fueled by a small group of anti-vaxxers in these neighborhoods. They have been spreading dangerous misinformation based on fake science.

Additionally, the World Health Organization has placed vaccine hesitancy, defined as "the reluctance or refusal to vaccinate despite the availability of vaccines", on its list of "Ten threats to global health in 2019".

  • Community wiki, so anybody can improve the answer. It's not entirely convincing right now. – Barry Harrison Apr 21 at 17:24
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    I'd say it's not an answer at all, but merely a statement by one person (albeit someone who likely has better information on the issue than most). – jwenting Apr 23 at 6:44
  • @jwenting Thanks for the comment. The Q was: "Is the comeback of the measles virus "largely due to anti-vaxers?" Have other sources made a similar attribution?" I guess "other sources with similar attribution" might count. If you want me to delete this, let me know. – Barry Harrison Apr 23 at 6:45
  • Your attempt at an answer covers the second part of the question, but not the first, I think. You probably should leave it as an avenue for further research or expand on it by digging into the sources used by these people to make their statements. – jwenting Apr 23 at 7:07
  • @jwenting I will edit to make this clearer. – Barry Harrison Apr 23 at 22:34

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