--chances are good you had *one* dose if you were born before the late 80s/early 90s when antivaxxers started making it easier to get non-religious exemptions from public school vaccine mandates, but if you don't want to count on that, go for the 2 doses. Otherwise one is probably okay.
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My mom wasn't antivax but she was a bit of a hippie who moved around a lot, so I suspect it's pretty likely I fell thru the cracks.