[landroverroy]

 I got it once, many years ago, and it never recurred. I assumed it was like smallpox and that once infected you were then immune. I actually didn't find it painful, just itchy, but it got infected and the redness started spreading up my arm so I had to go to the doctor and get some antibiotics.
 However, I would google it if I were you and get the full tale as expressed by the "experts".

[Black Sheep]

This:

http://emedicine.medscape.com/article/1133450-overview#a3

says "patients ... must also be informed that recurrences may occur but generally result in lesions that are less pronounced than the primary infection." and this:

https://www.cdc.gov/poxvirus/orf-virus/animals.html

says "Animals can become infected more than once in their lifetime but repeat infections usually occur after a year's time and are generally less severe."

Other sources suggest that this could be because the antibodies produced are not great at preventing re-infection (as opposed to limiting the severity/duration of a re-infection).

However this wouldn't look to be a spontaneous recurrence (like say shingles) but a re-infection, but since the references mention that the virus can stay active in the environment for months on inert objects it would seem quite feasible to be re-exposed without knowing about it (i.e. not just from contact with a symptomatic animal).

[SallyintNorth]

I believe that in theory you should be immune having had it once - but like all these things, the bugs don't read the books...