What shingles actually is
Shingles is chickenpox coming back. The virus never leaves after a childhood infection - it lies dormant in nerve tissue for decades and can reactivate when immunity dips with age, illness or stress. It emerges along the path of a single nerve, which is why the rash appears as a band on one side of the body and stops abruptly at the midline.
The rash clears in a few weeks. The problem is what can follow it: post-herpetic neuralgia, nerve pain in the same area that outlasts the rash by months and occasionally years. It is the complication that makes shingles worth preventing rather than treating, and the risk of it climbs steeply with age.
Check the NHS first - we mean it
Shingrix is offered free on the NHS to people in a defined age bracket, and separately from age 50 to anyone whose immune system is significantly suppressed. The age bracket has been widening in stages, so the honest answer is that it changes: ask your GP surgery whether you are in it this year before paying us.
We would rather tell you that than take £430 from someone who was entitled to it for nothing. If you are outside the bracket and do not want to wait several years for it to reach you, that is when paying makes sense.
Two doses, and the second one matters
Shingrix is given as two injections, the second between two and six months after the first. One dose on its own is not the course - protection from a single dose falls away far faster, and the trial evidence behind the vaccine is for two.
It is not a live vaccine, which is why it can be used in people whose immune system is suppressed. It is also noticeably more reactive than most: a sore arm, tiredness and aching for a day or two are common rather than unusual, and that is the immune response doing what it is supposed to.