I have always found myself impulsively and automatically spelling "anti-vaxxer" with two 'x's, and a Google search indicates that most other media sources did the same; however, I can't think of any other words in English that contain two adjacent 'x's, and I also can't think of a good consistent rule that would explain why it seems that the 'x' should be doubled in this case.

The person who reads is a "reader", not a "readder". However if I were to make up a word "to zif", then "the person who zifs" would probably be a "ziffer". In that case, you need the extra 'f' to distinguish the sound from something that rhymes with "lifer". Maybe the reason for the double-'x' is then that "anti-vaxer" might be mispronounced as "anti-vaikser"?

Anyone understand what is going on here? Are there other words that have an unusual but customary consonant doubling like this?

Update: other example: "doxxed"; also possibly related: "savvy" (from Fr. "savoir")

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    X, W, Y (and maybe some other letters) don't usually get doubled in English words. Nov 10, 2020 at 7:18
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    I've seen "anti-vaxer" with one x on quite a few occasions, and that's how I spell it.
    – nnnnnn
    Nov 10, 2020 at 8:17
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    Those who attempt answering by analogy need to remember that the syllable -vax- is clipped from words with no x at all. Nov 10, 2020 at 21:44
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    I can't find evidence to back this idea up, so just a comment: perhaps the two c's in vaccine changed to two x's.
    – paw88789
    Nov 13, 2020 at 2:46

5 Answers 5


Just to highlight how unusual the [xx] spelling is, the Dictionary of the British English Spelling System (Greg Brooks, 2015) has this to say about the double-letter [xx] in English:

Doubled letter: (does not occur)

Indeed, [x] is like several other consonant letters that are "never or almost never written double": [h, j, q, v, w, & y] (p. 110). Only one exception is noted for [xx]: the brand name Exxon. (For another name, there's also the classic arcade game Zaxxon.) Anti-vaxxer, presumably, is too new or too slang to appear in this spelling dictionary. According to Merriam-Webster editor-at-large Peter Sokolowski, it was first introduced to the dictionary in 2018, and it was first used in 2009 [Snopes]. Understanding its early history may illustrate how the spelling developed.


Vax before the first usages of anti-vax was mainly an abbreviation used to brand specific vaccines (e.g. M-Vax, YF-VAX). I can find no instances of use outside of the medical community.

Anti-vax to Anti-vax(x)er

Selective search results for anti-vax on Google and JSTOR first yield results between 2005 and 2010. The initial usages occur in medical contexts as shorthand for people opposed to vaccinations:

The final group is those that are zealously anti-vaccination (anti-vax). (Stephen M. Perle and Randy Ferrance, "What's Good for the Goose Is ... Ethics and Vaccinations." *Dynamic Chiropractic, 23.4, 12 February 2005.)

The usage would slowly leak into the larger scientific and skeptic communities. By 2009, a skeptics conference called The Amazing Meeting had a session titled "Anti-Anti-Vax Panel: Steve Novella, Joe Albietz, Harriett Hall, Michael Goudeau" on its schedule (James Randi Educational Foundation). At around the same time, anti-vaxer and anti-vaxxer make appearances in the comment section to neurologist and skeptic Steven Novella's Neurologica blog post titled "A Personal Attack By J.B. Handley" (22 April 2009). Joseph writes:

Anti-vaxer anecdotes rarely make sense.

And cheglabratjoe writes:

Of course, creationism probably isn't going to directly kill anyone, so these antivaxxers are far more dangerous.

The use of both forms, together, within a day suggests that, early on, both forms were in use.

A post later that year from another skeptic group (Australian Skeptics) highlights how skeptics propagated the word: "The 2009 Richard Dawkins Award Goes to Bill Maher, Anti-Vaxer":

Decide for yourself, but we think the only way to fight the scourge of the anti-vaxers is to ensure they do not get a platform in the mainstream media.

Other comment sections from the period also attest to both forms being in use.


Between 2009 and today, the word has entered general discourse. It is used by both proponents and opponents of child vaccination. For some reason, anti-vaxxer became the preferred spelling, the one that Merriam-Webster selected and most editors went with.

The reason why is arbitrary. Editors and dictionaries usually like consistency, so they tend to choose one form. We could argue various formal explanations for why the form does or doesn't make sense, but it's hard to generalize from such an unusual form.

Finally, at the end of my process I found a Grammarphobia blog post that confirms the gist of this answer, while also including a meditation on why the [xx] spelling caught on over the [cc] spelling:

Why are the spellings “anti-vaxxer” and “anti-vax” more popular than “anti-vaccer” and “anti-vac”? Our guess is that English speakers prefer “xx” and “x” because it’s natural to pronounce them like the “cc” of “vaccine,” while “cc” and “c” could be pronounced like the “c” of “vacuum.”


I don't think it's likely that "vaxer" would be misread as sounding like "vakes-er". All of the normal existing words with similar spelling (such as wax, ax, tax) are pronounced with short a and never double the x before a vowel-initial suffix.

A related previous question: Why do we write "fixing" instead of "fixxing"?

Also related: Should it be "doxxed/doxxing" or "doxed/doxing"?

If anything, I think xx in anti-vaxxer might be related to it being an abbreviation. That is something that it and dox(x)/doxxing have in common. But I don't know why double xx would be used specifically in abbreviations.

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    "xx in anti-vaxxer might be related to it being an abbreviation." This might go some way to explaining how come people started spelling it with xx, but it doesn't prove that the xx was the only or best option. Another word which ends with x even though it is a contraction of a word with no x is fax, from facsimile, yet we have faxed, faxing according to the more prevalent pattern of final x not doubling.
    – Rosie F
    Nov 10, 2020 at 8:15
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    Thanks, the "doxxed" page gives another example: "exxed out", which somehow reads better and with less phonetic ambiguity than "exed out" (which just looks bizarre, and suggests the wrong pronunciation of "eeksd out" or "eksid out"). However "all my exes" always uses the singular 'x'. And "He axed his plans" would never be written "He axxed his plans". Probably this all just comes down to what looks more natural in each case, for inarticulable reasons. Nov 11, 2020 at 7:41

If you expect English spelling to obey rules, you will often be disappointed.

This Ngram is for American English.


The British English Ngram shows only "vaxer".

Ngram does show both "doxxing" and "doxing" in both British and American.


There is absolutely no reason to double the x in vaxer, vaxing, or vaxed. There is no precedent in English for a double-x. Boxer/boxing/boxed, faxer/faxing/faxed, waxer/waxing/waxed, fixer/fixing/fixed, mixer/mixing/mixed, etc, are standard English.

Even vACCEr would be more ACCEptable than vaxxer: we have ACCEnt, ACCEss, ACCElerate, and so on, not axxent, axxess, and axxelerate.

Stop the madness!

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    "Stop the madness" can be applied to so many bizarre aspects of how English is used in day to day life... but we have even the NYT using the "anti-vaxxer" spelling at this point, so good luck in your quest! nytimes.com/2021/05/02/us/… May 25, 2021 at 1:21
  • Does "Stop the madness" refer to the current global program of vaccination against the COVID-19 virus? Or is it your objection to an extremely trivial point in spelling and only hyperbole? Jun 6, 2021 at 22:01

It's a colloquial term with colloquial etymology. It's supposed to have broken english, it's intentional.

The double x is a deviation from proper english in order to tap into the connotations of how the english language can be weaponised in the cultural context in order to associate a particular stereotype with a word to make anti-vaxxer a pejorative to deem it a negative term.

This is also known as newspeak, where the meaning of words is distorted in order to restrict the range of thought. Instead of using the term "vaccine hesitant" the mainstream media, government and dominant culture uses the term "anti vaxxer" instead, to polarise the debate, and frame the debate to show the logical fallacy and scaremongering of "you're either with us or against us". Someone with moderate or ambivalent opinions will be placed in the same category as someone with strong and assured opinions.

As multiple x's are colloquially used in english to show how extreme something is, in this case, it's the person holding such opinions who are considered extreme, not the people getting vaccinated and not how strongly an anti-vaxxer trusts and holds their opinions. So by using two x's instead of one, it's a way of mocking anti-vaxxers to show how eXXXXXXXXtreme they are. Extreme as in stupid, farfetched, crazy and ridiculous.

This is similar top how technology companies are changing the terms they use for git repositories and password managers from using the words master and slave to be replaced with primary and secondary.

The merits and premise of this is debatable.

  • My answer isn't rude or abusive. I never called anti-vaxxers those things. I said that that's the impression having two x's in the word instead of one, conveys. For one to explain how two x's in the word makes it a pejorative (which the OP seems to not be aware of), one must then explain what negative stereotype is associated with the pejorative.
    – desbest
    Jun 7, 2021 at 0:44
  • It's not enough to define a pejorative using its literal meaning (ie. against vaccines) because the OP already knows that, but also to describe the connotations that the pejorative entails. I was talking figuratively, not literally. If you thought the part you quoted in your comment was my opinion or soundbite, then you're mistaken and mis-read.
    – desbest
    Jun 7, 2021 at 0:51
  • You could replace the part I quoted with something innocent with neutral charge yet off key like "uses a straw to drink from a can" or "walks with the clothing tag still on their clothes" and my answer would still be valid, just that something had to suggested to denote the level of extremity the thing holds as a comparison or equivalent.
    – desbest
    Jun 7, 2021 at 1:05

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