A person’s response to vaccination is not associated with birthmarks or the presence of mutations in a gene involved with vitamin B9 production
Every person has a gene that produces an enzyme called methylenetetrahydrofolate reductase (MTHFR gene), which converts folic acid into its active form folate, also called vitamin B9. This gene helps repair DNA and remove free radicals. People with some rare mutations in the gene may have an increased risk of developing skeletal and neurological problems or blood clots, due to a reduction in MTHFR enzyme activity. However, most of the common MTHFR mutations either do not affect enzyme activity or only require individuals with the mutation to supplement their diets with folic acid. No scientific evidence supports the claim that mutations in the MTHFR gene are associated with either birthmarks or a higher risk of adverse reactions to vaccines.
Incorrect: Birthmarks are not indicators of mutations in a gene that codes for an enzyme called methylenetetrahydrofolate reductase (MTHFR gene) or any other genetic condition. Mutations in this gene, involved in vitamin B9 production, are also not associated with a higher risk of adverse effects of vaccines. Some rare mutations in the MTHFR gene lead to a metabolic disorder, but most of the common MTHFR mutations have little or no impact on human health.
Misrepresents source: The claim misrepresents findings from a single study to incorrectly associate mutations in the MTHFR gene with adverse effects from vaccination. The authors of the study denounced the inappropriate use of their article to support medical exemptions to vaccination in children who have variations in the MTHFR gene.
A Facebook post from mid-November 2018 went viral in late August 2020, receiving tens of thousands of interactions on Facebook. The post incorrectly claims that birthmarks are “indicators” of the presence of the methylenetetrahydrofolate reductase (MTHFR) gene, involved in the production of vitamin B9, and that the gene is associated with a higher risk of adverse reactions to vaccines. Because the MTHFR gene is present in every person, the author of the post is likely referring to mutations in the gene, rather than the gene itself. While some rare MTHFR mutations are the cause of a metabolic disorder, most of the mutations in this gene are very common among the population and do not represent a health risk. As we explain below, there is no scientific evidence that mutations in the MTHFR gene are associated with the presence of birthmarks or a higher risk of adverse reactions to vaccines.
The MTHFR gene produces an enzyme that converts folic acid, which occurs naturally in food, to its active form folate, also called vitamin B9. Folate is essential for DNA repair, eliminating free radicals, and methylation, a process that helps regulate protein production. Specifically, folate converts the amino acid homocysteine into other amino acids involved in methylation and in the production of the antioxidant glutathione. Folate deficiencies can lead to the toxic accumulation of homocysteine in the blood (hyperhomocysteinemia), which may increase the risk of spina bifida, a birth defect in which the spine and spinal cord do not form properly, as well as blood clotting and a variety of skeletal and neurological problems.
People who have rare mutations in the MTHFR gene can experience increased homocysteine levels in their blood due to reduced MTHFR enzyme activity. However, for people with other common MTHFR gene mutations, homocysteine levels in their blood are either unaffected or only increased when they have a dietary deficiency in folic acid. Contrary to the post’s claim, genetic testing has minimal clinical utility, and the diagnosis of hyperhomocysteinemia relies on a blood test that measures total levels of homocysteine. However, genetic testing may be used to confirm the diagnosis of an inherited hyperhomocysteinemia caused by MTHFR deficiency.
Also contrary to the claim, there is no scientific evidence that birthmarks, such as stork bites, sugar bugs, and sacral dimples, are indicators of mutations in the MTHFR gene. These skin marks result from the overgrowth of blood vessels or pigment cells, but the cause of such overgrowth is unknown. In general, birthmarks are harmless and fade over time without requiring treatment. However, experts recommend monitoring birthmarks that are large, located along the spine, or interfere with normal activity.
There is also no scientific evidence to support the claim that mutations in the MTHFR gene increase a person’s risk of adverse reactions to vaccines. This claim is likely based on a single study published in 2008 in the Journal of Infectious Diseases exploring whether one mutation in the MTHFR gene increased the risk of adverse effects to an experimental vaccine against smallpox. While the study authors observed local inflammation at the site of injection, fever, rashes, and lymph node swelling in 24 out of 46 participants, they did not report any severe or long-term effects. The authors also wrote a 2019 letter clarifying that their research should not be used as evidence for an association between the MTHFR gene and an increase in adverse reactions to vaccines after several people misinterpreted their results. The letter states, “[t]he study was a small, underpowered, exploratory, candidate gene study conducted [more than] 15 years ago in a special population—participants in 2 small phase 1 studies of smallpox vaccines. This article does not meet the standards for establishing a robust genetic association”.
The authors also pointed out that their study involved an experimental vaccine that was in clinical trial and not approved by the U.S Food and Drug Administration (FDA). In addition, the vaccine was for smallpox, which was eradicated in 1980. Calling attention to the inappropriate use of their study to justify vaccine exemptions, the researchers stated in their letter that:
“The citation of this exploratory report, which addressed a unique set of phase 1 studies of a candidate smallpox vaccine, should not constitute an exemption from formal vaccination recommendations issued by the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices. […] It is unfortunate that the loose application of our exploratory report has been misinterpreted and used to inappropriately justify exemption of children from medically indicated vaccines.”
In summary, there is no scientific evidence to support the claim that mutations in the MTHFR gene are associated with birthmarks or a higher risk of adverse events from vaccines. While some people with rare mutations of the MTHFR gene have an increased risk of blood clot formation and skeletal or neurological problems, most mutations do not affect a person’s health.
- 1 – Forman et al. (2009) Glutathione: Overview of its protective roles, measurement, and biosynthesis. Molecular Aspects of Medicine.
- 2 – Škovierová et al. (2016) The Molecular and Cellular Effect of Homocysteine Metabolism Imbalance on Human Health. International Journal of Molecular Science.
- 3 – Varga et al. (2005) Homocysteine and MTHFR Mutations: Relation to Thrombosis and Coronary Artery Disease. Circulation.
- 4 – Hickey et al. (2013) ACMG Practice Guideline: lack of evidence for MTHFR polymorphism testing. Genetics in Medicine.
- 5 – Reif et al. (2008) Genetic Basis for Adverse Events after Smallpox Vaccination. The Journal of Infectious Diseases.
- 6 – Reif et al. (2019) Inappropriate Citation of Vaccine Article. The Journal of Infectious Diseases.