Shingles occurs as when you get chickenpox the virus (varicella) stays in in your system and can occur years later as shingles along nerve lines. Yes it is very painful -just had it in August 2016 whilst overseas and developed secondary bacterial infection in one nodule. Took 10 weeks for nerve pain subside enough, to come off medication for this pain. Then 2 weeks later had routine screening mammogram and then got my BC diagnosis 3 weeks later just before Christmas!!
2016 not my favourite year!!
Shingles vaccine is now free for over 70s but costs for other ages except some health groups I think. Talk to GP or public health unit before having vaccines to discuss avisability in your own case before having it to rule out any risks especially if presently undergoing any treatments.