If you had chickenpox as a child, the virus that caused it can re-emerge later in life —to cause shingles. This condition, also known as herpes zoster, consists of a rash on one side of the body, often accompanied by excruciating pain. The rash typically goes away in about a month, but in some people, the pain lingers for weeks, months, or even years. This chronic pain is called post-herpetic neuralgia. A vaccine called Zostavax can help prevent shingles. It is recommended for people ages 60 and older. The vaccine is produced by treating live varicella-zoster virus in ways that weaken it but don’t kill it. Though Zostavax works reasonably well to prevent shingles, it tends to be less effective in older people. And because it contains live virus, it should not be given to people with weak immune systems. An experimental new vaccine which goes by the name HZ/su, just described in The New England Journal of Medicine, seems to get around these problems. In the international Zoster Efficacy Study in Adults 50 Years of Age or Older (ZOE-50), the new vaccine appeared to be effective even in older people. It may, however, cause more pain at the injection site and also more frequent muscle pain and headache than the current vaccine. Even if the new vaccine performs well in future tests, FDA approval would still be a few years away.