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MTHFR and Vaccines

This is a subject I get questions about almost daily, and the internet is filled with opinions, threatening pieces, and loud voices. But what is the truth?

General Thoughts about Vaccines

I know there are many strong opinions about vaccines out there, and I want to clarify my underlying views before diving into the specifics about MTHFR and vaccines. First, let me say this. I’m pro-vaccine. I know many of you may be offended by that, and I am sorry, but at the end of the day, vaccines have saved millions and millions of lives that might otherwise have been lost.

My uncle contracted polio as a child and had to spend months in an iron lung – I wouldn’t wish that one any human. Tetanus is still largely untreatable and extremely easy to contract, but it’s easily preventable. Smallpox has been eradicated from North America because of vaccines. These facts are nothing to scoff at and, in my opinion, make vaccines a largely beneficial public health measure.

Are there things that aren’t done exactly right in vaccines? Well, yes. Of course, there are. For decades vaccines in multi-dose vials were preserved with thimerasol, which is essentially mercury. I am not into injecting mercury into any human, least of all babies. There are other preservatives that I’m not a fan of mainlining, including phenol, a chemical used in medical research to induce tumors.


Additionally, the list of excipient ingredients in vaccines reads like a horror show. Formaldehyde? Check. Aluminum salts? Absolutely. Polysorbate 80? Sure, toss some in. A complete list of vaccines and their excipient ingredients in the U.S. can be found here.

So – I’m not saying they’re all hearts and flowers, but I am saying they’re better than childhood polio.

Still, vaccines are a very personal decision and should be made with as much information as possible about the risks and benefits of both the vaccine, your risks and family history, and the disease it can prevent.

MTHFR and Vaccines – Adverse Event Reporting

Within the MTHFR community and the internet at large, we all suspect that MTHFR folks could have more trouble than average with vaccines. This idea is logically derived from the fact that people with an MTHFR mutation have a harder time than average eliminating heavy metals, which matters in light of the aluminum and mercury content. Also, people with MTHFR have a higher tendency toward blood clots when our methylation is unbalanced, and homocysteine is high. So well-managed MTHFR does not increase the risk of clotting, but poorly managed MTHFR with high homocysteine does.

Research on this subject, however, is extremely limited. It just hasn’t been done, so the objective data isn’t here yet. Even a search of the US Vaccine Adverse Event Reporting System yields very little fruit. This is in part because most people who have MTHFR, are unaware that they have MTHFR and may not report that when they create an adverse event report. Also, in the grand scheme of things any knowledge about MTHFR is reasonably new.

In the VAERS (Vaccine Adverse Event Reporting System), five adverse events are reported in clients with known MTHFR. In one, the TDAP vaccine, produced extreme fatigue that interfered with the ability to work. One reaction in a child born to a mother given the DTaP vaccine in the 8th month of pregnancy had extreme eczema. The others were to the Covid-19 vaccine in its various forms and included severe flu-like symptoms, exacerbation of chronic fatigue, and a short-term allergic reaction.

The adverse events are all self-reported, and what information the patients share about their clinical history is entirely self-directed, so it’s hard to draw conclusions from this information.

MTHFR and the Smallpox Vaccine

The Journal of Infectious Disease actually conducted a study looking at adverse events to the smallpox vaccine and various genetic polymorphisms. In this study, MTHFR polymorphisms were associated with adverse event risk in two separate trials, which is certainly significant. This is the best and most relevant evidence that people with MTHFR polymorphism might have to be cautious, but of course, this only tests one vaccine and not the rest of them. It is a start, but it is unwise to generalize to all vaccines because of one study on one vaccination.

MTHFR and Blood Clots after the Covid-19 Vaccine

The other useful study is a case report published in the Journal of Neurology about two young women with MTHFR polymorphisms who developed blood clots after the AstraZeneca Covid-19 vaccine. Both of these women did have MTHFR polymorphisms but they also had a perfect storm of clotting risk factors that can’t be overlooked.

In the case of these two women, MTHFR can contribute to clotting, both were taking estrogen-based birth control pills, which increase clotting risk, both had a prior history of deep vein thrombosis (which are clots), and the vaccine itself is for a virus that is known to increase clotting risk.

These two patients certainly had adverse events related to the vaccine, and MTHFR was one contributing factor, but other factors can’t be overlooked.

MTHFR and Blood Clots after the Covid-19 Vaccine
MTHFR and Blood Clots after the Covid-19 Vaccine

MTHFR, Vaccines, and Autism Risk.

There is a known increase in the risk of Autism for people with MTHFR variants and mothers who had high levels of folic acid supplementation during their pregnancy – you can read all about that here. There is also an increased risk with heavy metal exposure and even possibly, albeit controversially, the MMR vaccine.

The data here doesn’t exist either – we don’t know if kiddos who get a full complement of vaccines and who have MTHFR have any different risk than kids with MTHFR who don’t get the full complement of vaccines.

In my mind, this comes down to a logical pro and con question – if your kiddos have many risk factors for autism, then it might make sense to be more cautious about adding other risk factors to that stack, including vaccines and their excipients. That includes avoiding environmental sources of heavy metals as well. This isn’t just about vaccines, this is about toxin avoidance, getting good nutrition, and doing what you can, including carefully considering vaccine options.

This is the last podcast episode for this season, and I thank you so much for being here and offering me ten minutes of your week. As usual, summer will be devoted to family and outdoors, but once school starts, we will be back for Season three. Look for a Season three trailer in the next few weeks – it is about a new and exciting topic, I”m collaborating with a dear friend and colleague, and I just can’t wait to get started.

Over the summer, there will still be new blog posts, including topics like keeping MTHFR kiddos healthy, best antidepressants for MTHFR, and signs of MTHFR in babies. Genetic Rockstars is in full swing no matter what, and you can join us there at Also, over the summer, Enrollment will be open for a beta test version of the course MTHFR for Life, which will start in the autumn. You can check that out at

Enjoy your summer, and I’ll see you in September.

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MTHFR is a common genetic mutation that can contribute to anxiety, depression, fatigue, chronic pain, infertility, and more serious conditions like breast implant illness, heart attack, stroke, chronic fatigue syndrome, and some types of cancer. If you know or suspect you have an MTHFR variant, schedule a free 15-minute meet-and-greet appointment with MTHFR expert Dr. Amy today.

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Amy Neuzil
Amy Neuzil

Dr. Amy Neuzil, N.D. is a leading expert in MTHFR and epigenetics, and she is passionate about helping people achieve optimal health and wellness for their genetic picture. She has helped thousands of people overcome health challenges using a simple, step-by-step approach that starts with where they are today. Dr. Neuzil's unique approach to wellness has helped countless people improve their energy levels, lose weight, and feel better mentally and emotionally. If you're looking for a way to feel your best, Dr. Amy Neuzil can help. Contact her today to learn more about how she can help you achieve optimal health and wellness.

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