Should you vaccinate your kids if they have the MTHFR mutation?

I recently read (for the millionth time) that anyone who carries MTHFR variants should not be vaccinated.  The reason given is that those with decreased MTHFR enzyme activity cannot detoxify or ‘handle’ vaccinations, often with references to mercury in the vaccines.

This article reviews the published scientific studies on the topic of MTHFR and vaccinations.

I am not weighing in on whether you should vaccinate. I  advocate for learning about all health topics and making decisions based on actual scientific evidence.

MTHFR Genetic Variants:

The MTHFR gene codes for the enzyme that plays a critical role in using folate in the methylation cycle. There are two genetic variants of MTHFR that many researchers have focused on. These two variants are known as C677T and A1298C. (Read more and check your 23andMe data here: How to check your genetic data for MTHFR.)

I purposefully refer to the genetic change in MTHFR as a variant instead of a mutation. At least one copy of the C677T variant is found in over half the people in most population groups. This is not a rare mutation.

Studies on MTHFR and vaccine injuries:

Researching the studies on MTHFR variants and vaccination injuries or adverse events lead me to exactly one study.  Seriously. One study on a vaccine that is no longer given.

It is an open-access article on genetic variants and adverse reactions to the smallpox vaccine.

Overview of the study: 
In a study conducted by Vanderbilt University, 131 people (average age of 23) received a vaccine for smallpox. The results showed that those individuals with an MTHFR C677T variant were more likely to have an adverse reaction to the vaccination. The study also linked other genes to an increase in adverse events.

Adverse events were defined as a skin reaction at the site of injection, fever within 30 days of the vaccine, or enlarged or tender lymph nodes.  40 study participants reacted to the vaccine and 69 participants did not.[ref] Smallpox vaccines have not been used on the general public in the US in over 46 years, and none of the study participants had previously received a smallpox vaccine. The vaccine contains a live virus that is similar to smallpox. It is given only to those who are at risk of smallpox exposure. [ref]

update! Read why the author of that study does NOT think it shows a reason not to vaccinate: article in The Atlantic.

What about studies on MTHFR and vaccine excipients?

Some claim that excipients added to vaccines are the reason that MTHFR C677T carriers should not be vaccinated.

I did find a small study (50 participants) showing that those with the MTHFR C677T variant might be more sensitive to mercury. The study looked at the genes of 25 participants that had been diagnosed as sensitive to mercury compared with a control group of 25. The MTHFR 1298C/C genotype was more common in the mercury-sensitive group. (Some may question the statistics here with such a small group size.)

But…   Mercury has been removed from children’s vaccinations since 2001 in the U.S.  Seasonal flu vaccines for those over 6 years old can still contain mercury, so check the ingredients on that particular vaccine.

I didn’t find any other links between MTHFR variants and other common excipients in vaccines.

A study on vaccines and MTHFR that (hopefully!) doesn’t apply to children found that a cocaine vaccine worked better for MTHFR 677T/T genotype (decreased cocaine use and depression scores).[ref]

Conspiracy theory and other genes:

The ‘conspiracy theorist’ in the back of my mind wondered if the link between MTHFR and vaccine injuries was just being covered up — or perhaps deliberately not studied.

But… that doesn’t seem to be the case.

I did find several studies looking at the interplay between genetics and vaccination reactions. There has been work done looking at genetic variants and the role they play in both the effectiveness of vaccines and in regards to adverse events; those studies do not mention MTHFR as being involved in vaccine events.

One study found quite a few HLA gene variants as well as other immune system gene variants that do play a role in how vaccines work. The study examined the response to measles vaccinations and found that HLA type predicted whether the recipient would have a strong or weak immune response to the vaccine.[ref] Another study found that CD46 genetic variants also influenced the response to the measles vaccine.[ref]

These immune system genes make sense to influence vaccine response — a lot more sense than the MTHFR variant.

Someday, hopefully, we will be at the point where those who are most susceptible to a disease will be able to get a vaccine that is genetically right for them – at the right time and in the right amount.

Summing up the evidence:

  • No real scientific evidence pointing to the common MTHFR variants playing a role in vaccination adverse events.
  • Carriers of the MTHFR C677T T/T genotype are possibly more likely to react mildly to the type of smallpox vaccine that was used over 10 years ago.
  • Other genetic variants that have been found to increase the risk of either adverse events or vaccine effectiveness.

More to read:

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15 Comments on “Should you vaccinate your kids if they have the MTHFR mutation?

  1. Thank you very much for this article, it has answered a lot of my questions. I too am interested in the science to prove what appears to be a connection.

    • I was also looking for evidence and could not find any scientific studies either. It seemed odd to me. Then I find myself questioning why there are none? I would like to become educated more on this topic because I believe there is so much yet to be discovered.

      • I still find it strange that something that is so vehemently ‘known’ on Facebook groups and forums has no basis in scientific studies. The only information that I find is from Ben Lynch’s videos. It is his theory, not based on any study other than the one older study on smallpox vaccines.
        It does make sense that MTHFR C677T and A1298C wouldn’t play a big role in vaccine injury though, because the variants are too common – covering more than half the population.
        So my big question is still to wonder why there aren’t more studies tying other, probably much less common genetic variants to vaccine injury. We know vaccine injury happens, so why isn’t there a push to predict who is at risk?

        • Some food for thought: Could we consider that 1 in 36 children are now being diagnosed with Autism. They qualifies as an epidemic…and would account for the 50% of the population discussed (actually more) above. Consider reading the book “How To End The Autism Epidemic” which covers this. A great, thought-provoking read with studies included. As an autism mom, it has taught me so much!

        • The MIND Institue in Sacramento, California has been studying this a long time. The lead researcher did a nice synopsis of the recent results of brain tissue studies (post mortem) and the research indicates that those with the MTHFR variant (he refers to it as a mutation) had greater amounts of mercury in the brain. Another brain tissue study looked at aluminum (aluminum salts are used as an adjuvant in vaccines) and that was also significantly higher than in the non autistic brain. I, like so many other parents of kids with ASD, just know our kid was fine before the vaccines and not fine after. I have spent my life since teying to support familes like mine. The simple truth is we don’t know what causes it. Did I vaccinate all my other children? (I have 8…3 after the one with ASD.) Yes, slowly and delayed but all had their shots by age 8. Did any of the others develop autism? Nope, although they have some features. Did any have weird adverse reactions to the vaccines? Yup! One got cystic infections with the DTaP.

          It may be a logical attribution error, but cause and effect is all we have to know at this point. The jury is still out on this one.

          • Hi Maria,
            Thanks so much for taking the time to post your comment on the MTHFR and vaccines article.
            Do you happen to have the name of the lead researcher at the MIND Institute that published on the MTHFR variant and mercury in the brain tissues? I’m having a hard time finding the study and would love to read it. I also would love the title or a link to the study on aluminum in the brain tissue – not sure if you are linking that to MTHFR or not?
            The first thing that comes up for the MIND Institute and vaccines is their position paper stating that vaccines are not linked to autism and that people should vaccinate their children:

  2. I have MTHFR C677T mutation and prior to knowing this started noticing that right after getting my annual flu shot I would become seriously depressed and emotionally detached. It was like I could feel nothing. It would be really bad for weeks but linger for months. I took a DNA test and ran the raw data through some programs and thats when I found out about the mutation. I also have ADHD and have been B12 anemic off and on I asked my psych if there could be a tie between the flu shot, the depression and the gene mutation. He laughed it off. I haven’t had the shot in 2 years and haven’t had the same issues. I wish I could find a doctor that would take the tests seriously and help me find solitions. I have been eating more whole foods and taking 5- MTHF and B-12 methylcobalamin which seems to help. I have less anxiety, am more focused and more energy.

    • Hi,
      It sounds like you are on the right track with getting more whole foods, folate and B12. I honestly don’t know how much the MTHFR variant plays a role in your reaction to the flu shot. There are probably quite a few different genes that are involved in your immune response to the vaccine and the additives in the vaccine. One thing to consider may be the timing of when you get the vaccine if it is in the fall/winter — could you be reacting to the change in seasons (SAD)? or could that be compounding the immune response that your body has to the vaccine? Whatever the reason, I’m glad that you are finding the solutions you need.

  3. I came across this article while looking
    Into vaccine injury as my questions are purely on a hunch. I have 3 children, two of which are MTHFRC-677T and one who is not. Both of the MTHFR children were immunized just like the other child but the MTHFR children both started showing signs of autism around 2 years old. I find it odd that one of the MTHFR children and one without are twins; one is autistic and the other is not. Any thoughts about this? Is it a coincidence or not?

    • Hi Angela,
      I haven’t found any research that links MTHFR and vaccines to autism.
      The question of whether the child’s MTHFR variant adds to the risk of autism has been looked at in several different studies, but the results don’t always agree. There was a recent Chinese study that showed no increased risk of autism with the MTHFR C677T variant ( but other studies did show it increasing the risk a little bit ( This may be due to different diets in the populations studied.

      What you may want to look at instead is the research on folate levels and the mother’s MTHFR status — and how that all interacts with the baby’s genetics. My guess (keeping in mind that I’m not an autism expert nor a doctor) is that autism is multifactoral – prenatal environment, baby’s genetic susceptibility, mother’s genetics, epigenetics, and the gut microbiome.

      Here are a couple of studies that you might find interesting: — this has a good section on how the microbiome (folate and B12 production from gut microbes) interacts with the methylation cycle as well as with MTHFR variants.

      Are you familiar with Dr. Amy Yasko’s work with the methylation cycle and autism?

      Best of luck to you as you continue your search for answers on this. Let me know if you need help with finding other research on the topic — I’m sure your online time is limited with three kids, two with autism and twins to boot!

    • Hi Lauren,
      Thanks for commenting and adding that study. Looks like that is a vaccine that is still in use in Australia, UK, NZ, and possibly Canada.

    • Thanks for adding these.
      Looks like both are reviews of studies on adverse events from vaccinations. The information on the MTHFR variant in both reviews is just referring back to that one single small study of the smallpox vaccine.
      Thanks for reading and commenting.

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