MTHFR and VaccinesI recently read, for the million-teenth time, that anyone with an MTHFR polymorphism should not be vaccinated.  The argument always seems to be that those with decreased MTHFR enzyme activity cannot detoxify or handle a vaccination. This seems to be accepted as fact by some, but I hadn’t really read anything other than anecdotes about it.  So I decided to look into the scientific studies on the topic.

**Note that I’m not weighing in on whether or not kids should be vaccinated on the currently advised pediatric vaccination schedule — just addressing the science behind MTHFR polymorphisms causing adverse reactions to vaccines **

Looking into the studies on MTHFR variants and vaccination injuries and/or adverse events lead me to exactly one study.  The study was small, with less than 200 people included in it.  It looked at several different polymorphisms as related to adverse events from a small pox vaccination.  It did find that those individuals with an MTHFR C677T polymorphism were more likely to have an adverse event.  It also linked a couple of other polymorphisms with an even greater likelihood of adverse events.   Again, though, this is a small study using a vaccination that is not normally in use today.  (Smallpox vaccines have not been used on the general public in the US for about 45 years.)

Could there be other studies on MTHFR and vaccination adverse events?  Possibly, but I couldn’t find any that have been published.  If you know of any, please leave a comment below.

Going after the idea that excipients in the vaccine are what cause those with MTHFR variants (i.e. half the population) to be harmed by vaccines, I did a very small study (50 participants) showing that those with the MTHFR C677T polymorphism might be more sensitive to mercury.  But that really isn’t much of an issue since mercury has been removed from children’s vaccinations since 2001.  (Seasonal flu vaccines for those over 6 years old can still contain mercury.)

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

In digging into the topic, I did find several studies looking at the interplay between genetics and vaccination reactions.  So 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, but 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 sums up: “We predict, based on the type of work discussed herein, a time when it will be possible to determine what diseases an individual is at risk for, what vaccine(s) they should receive, at what doses and the chance that they may experience any significant adverse event. This is a very different experience than the current situation where essentially everyone gets every vaccine, given in the same manner, at the same dose and same number of doses – ignoring the reality that we are genetically preprogrammed to immunologically respond in predetermined differing patterns.”

To sum it up:

There is not a lot of evidence pointing to common MTHFR polymorphisms playing a role in vaccination adverse events.  There are other genetic variants that have been found to increase the risk of either adverse events or vaccine effectiveness.  I’ve listed some of the studies below.   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.

More to read:


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