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Vaccines- Fact Check it!

Vaccines- Fact Check it!

Hello everyone,

Each month Metafact members vote on a topic for us to investigate with the world’s top experts. We call these Metafact Reviews - and they are science-powered guides giving you the state of knowledge today.

Our launch review last month was on Vaccines - a topic plagued with internet misinformation and weaponized by technology companies. Today we have opened up our findings for everyone to read and share. From questions on supposed toxic ingredients to autism, herd immunity and the HPV vaccine - we want everyone to learn from what we’ve found with over 50 of the world’s top immunologists and public health experts.

To help our members and supporters, I have started recording an audio version of each review for those who prefer it, or want to listen while traveling, ironing or in the shower… If you don’t want to miss a recording, you can subscribe to the Fact Check it! podcast on SpotifyAnchor or Google.

Let me know what you think in the comments below and by all means share this to friends, family members and colleagues interested in signing up to the Verified newsletter:

Enjoy our vaccines review and always remember…

May the facts be with you!

Ben McNeil

Founder, Metafact

The most damaging medical hoax of the 20th Century

In 1998, the medical journal The Lancet published an article titled “Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children.” Authored by British doctor Andrew Wakefield and 11 coauthors, the article purported to find evidence that the MMR vaccine -- which targets measles, mumps, and rubella -- caused autism and gastrointestinal disorders.

In the years following the publication, hundreds of studies demonstrated no link between vaccines and autism, and scientists harshly criticized Wakefield’s methodology and his failure to disclose conflicts of interests. In 2010, The Lancet fully retracted the original article and Wakefield was stripped of his medical license that same year.

But by then, the damage was already done. Many parents, fearful of causing their children to develop autism, refrained from vaccinating them, and we’re now treated to regular headlines of measles and mumps outbreaks among children. The journal The Annals of Pharmacotherapy characterized Wakefield’s study as "perhaps the most damaging medical hoax of the 20th Century.” Despite the paper’s retraction, vaccine misinformation continues to proliferate and social media and the “anti-vaccination” movement are showing no signs of slowing down.

Because of the wide dispersal of misinformation, it’s important to hear directly from the experts about the importance of vaccinations. That’s where Metafact comes in. In this week’s review, we hear from a range of scientists across the globe about vaccine side effects, supposed toxic ingredients, and the safety of herd immunity. Stay tuned...

Of milkmaids, kings and Edward Jenner

In 1796, London was gripped with fear. One in five of deaths came from smallpox, a contagious air-borne virus that would cripple the immune system. Smallpox dates back thousands of years. The mummy of Egyptian King Ramses V, who died in 1157BC, was found to bear the trademark rash. It kills approximately one in three of those infected. Today, smallpox is famous for being the first disease that humankind eradicated from the planet. This immense achievement came about from a serendipitous discovery in country England.

In the 18th century, something curious happened to milkmaids in the English countryside. They would never get smallpox. In 1762 a milkmaid gloated to a curious boy that “I shall never have smallpox for I have had cowpox [and] I shall never have an ugly pockmarked face”. The teenager was Edward Jenner who later became a doctor.

In 1796, Jenner tested the milkmaid idea. He infected eight-year old James Phipps with cowpox using pus gathered from the blisters of Sarah Nelmes, a milkmaid. He then exposed Phipps to smallpox and noticed he didn’t contract the virus. Once vaccinated, a patient develops antibodies that make them immune to not only cowpox but smallpox too. The Latin word for cow is vaccus while cowpox is vaccini; so Jenner coined the term ‘vaccination’ to describe the technique.

In the 1870s, French scientist Louis Pasteur developed a similar method to protect people against Rabies and Anthrax. In honor of Jenner, he called the preparation a ‘vaccine’. (Some dispute the Milkmaid story and claim John Fewster should take more of the credit).

Discovering vaccines was huge — getting vaccines to millions was the next challenge. In 1967 smallpox was still killing up to 2million people in the poorer parts of the world. The World Health Organisation invested US$100million over the next 10 years. In 1977, the last person to ever get smallpox was Ali Maow Maalin, a Somalian hospital cook. Smallpox was the first, but now vaccines protect many diseases.

The Consensus

Do vaccines cause Autism?

Despite the retraction of the Lancet article, there’s still widespread suspicion that vaccines actually do cause autism. So what evidence do we have that they don’t?

Our experts were unambiguous in their rulings on this topic. “There is absolutely no single shred of evidence that vaccination, of any type, causes autism,” wrote Mark Pepys, professor of medicine at University College London. “There is also absolutely no shred of scientific evidence about either vaccination or autism suggesting any possible mechanism that could be responsible for such an association.”

One claim made by the anti-vaccination is that the preservative thimerosal, which was once used in some vaccines, contained mercury and led to adverse effects, including autism. But studies couldn’t find any evidence of this, and thimerosal was later removed from most vaccines out of an abundance of caution. “The rates of autism have risen in the US after the thimerosal was removed, further supporting the safety of the vaccines,” noted University of Pittsburgh associate professor Richard Zimmerman. “Something else must be causing autism if children are getting it despite thimerosal’s removal.”

Indeed, scientists like Dwight German, a professor at UT Southwestern Medical Center, have engaged in animal studies to determine whether such effects exist. “We recently studied the brains and behavior of non-human primates, exposed to the same human childhood vaccination schedules to determine whether neurodevelopmental changes occur,” he wrote. “... We found that the vaccines/thimerosal caused no behavioral or brain abnormalities that are characteristic of ASD.” How could a vaccine not cause harm if it contains mercury? As Amelia Warren, an expert at Bond University, explained, “the amount of organic mercury found in a single serving of tuna (e.g., one can) is equivalent to the amount found in a single vaccination shot.”

Are there toxic ingredients in vaccines?

We’ve established that mercury doesn’t pose a threat. But what about the other ingredients in vaccines? Are any of them toxic?

All of our experts agreed they’re not toxic. While it’s common for vaccines to cause some inflammation and soreness, this doesn’t mean they’re toxic, and most governments closely monitor the industry to detect any potential problems early on. “There are surveillance systems in place to monitor vaccine-related adverse events,” wrote Kate Zinszer, an expert from Université de Montréal. “The risks of adverse events greatly outweigh the benefits vaccines provide at the individual and community level. To ensure the safety of vaccines, federal agencies in Canada, the US and worldwide routinely monitor and conduct research to examine any new evidence that would suggest possible problems with the safety of vaccines.”

Do I need to get vaccinated if everyone else is?

When reading about vaccines, you’ll likely come across the term “herd immunity,” which describes the phenomena by which diseases have a difficult time spreading in populations where vaccine rates are high. In this scenario, an unvaccinated individual would be unlikely to contract a disease because everybody they come into contact with is immune to it.

This has led some to wonder whether it’s worth getting vaccinated if you live in an area with vaccination rates above 90%.

All of Metafact’s experts agreed that you should still be vaccinated. For one, if everyone adopts the position that herd immunity will protect them, then that would naturally lead to less herd immunity. “If an individual decides that he/she, or their child is protected because of the 'firewall' and therefore has such a low chance of getting the infection that they decide not to bother getting the vaccine, then they do not contribute to the firewall, creating a small crack in it,” wrote Michael Mina, an assistant professor of epidemiology at Harvard. “At a population level, it is likely that their decision was either informed by or will inform other people's decisions to not vaccinate for the same reason. And very quickly, the firewall will contain many cracks because many people think that there is no need.”

What’s more, a vaccination rate is just a rough generalization and doesn’t really reflect your chances of encountering an unvaccinated individual. “The estimate is representative of a closed population where susceptible individuals are scattered evenly throughout,” wrote cancer epidemiologist Michaela Hall. “In practice, the population is not closed, many people travel to and from other countries without high MMR vaccine coverage rates and additionally, unvaccinated individuals are often concentrated within local areas or groups, meaning that herd protection may be significantly reduced in some areas.”

Also, if a disease is highly contagious, then a much higher vaccination rate is required to reach herd immunity. “In a totally susceptible population, one person infected with measles on average infects 20 other persons,” explained Cornelis H van Werkhoven, an expert at University Medical Center Utrecht. “The World Health Organisation (WHO) recommends that, in order to prevent spread of measles in the population, over 95% of the population should be vaccinated.”

Is the HPV vaccine safe?

The HPV vaccine, which vaccinates one from certain strains of the human papilloma virus, was introduced to the population in 2006, and it’s recommended by the World Health Organization because of its ability to prevent cervical cancer.

Given its relative newness, some Metafact users have wondered if it’s safe.

All the Metafact experts agreed that it was. “Over 80 million doses of the vaccine have been administered around the world and safety has been closely monitored by a number of organisations,” explained University College London cancer researcher Jo Waller. “All have concluded that the HPV vaccine is safe.” Gregory D. Zimet, a professor of pediatrics at Indiana University School of Medicine pointed to a study comparing unvaccinated females to vaccinated females that “failed to find any differences in rates of multiple sclerosis or other demyelinating diseases.”

Zimet noted that, though it’s impossible to eliminate all risks pertaining to vaccines, they’re still overwhelmingly safe. “HPV vaccination is not 100% safe, but no activity in life is 100% safe, even getting out of bed in the morning. However, we can say with 100% certainty that getting vaccinated against HPV is safer than not getting vaccinated and that vaccinating a child against HPV is safer, for example, than having a child ride in a car wearing a seatbelt.”

Quick Answers

Do multiple vaccines overload the immune system? Extremely unlikely. As one of our experts put it, "a baby could theoretically respond to 10,000 vaccines at once."

Is a universal flu vaccine possible? Maybe. "There is a theoretical possibility to vaccinate against targets common between strains, using novel immunological approaches."

Is the influenza vaccine effective? Yes. It's not 100% effective, but it significantly reduces your chance of getting the flu.

Does the HPV vaccine increase risk of blood clots? No.


  1. There's no evidence that vaccines cause autism. So don't believe what celebrities tell you.

  2. Sure, vaccines come with risks from adverse reactions, but nearly everything you do has some risk involved. Bottom line: the risks posed by not getting vaccinated are far greater than the risks associated with vaccines.

  3. Herd immunity helps protect you, but don't let it serve as a stand-in for getting vaccinated.

  4. Don't believe anti-science celebrities and activist claims on Facebook or Youtube. Opinion is free, but facts are sacred. Ask Metafact first here.

  5. Throughout their history, vaccines have saved millions of lives. Maybe even your own. So enjoy your life!

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