I was diagnosed on March 28 and got the vaccine on April 26 (after lesions were gone). My Doctor checked and said I didn't have to wait until the pain subsided; it was more important to get the vaccine.
According to my Doctor the vaccine reduced the incidence of shingles returning by 61%, and reduced the incidence of postherpetic neuralgia by 66%. I liked those odds.
Originally my insurance did not cover the vaccine because I was younger than 60 years of age. When I challenged the denial, they ended up paying for it since there was a change in policy adding the coverage of individuals 50-59 to the coverage.