If you had chickenpox as a child, the virus that caused it can re-emerge later in life — out of the blue — 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.
The virus that causes chickenpox, known as varicella-zoster, doesn’t necessarily disappear from the body after the chickenpox rash fades away. Instead, the virus can go into hiding, taking up residence in the nerve roots coming off the spinal cord. As the immune system becomes weaker with age, varicella-zoster may “wake up,” start to grow in a nerve root on one side of the body, and cause shingles.
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. This is what’s known as a live attenuated vaccine. 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. This vaccine consists of just a single protein of the virus. Zostavax contains all of the viral proteins.
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.
HZ/su still faces more testing. The University of Colorado, for example, has mounted a head-to-head test of Zostavax and HZ/su in younger (ages 50 to 59) and older (ages 70 to 85) adults. And even if the new vaccine performs well, FDA approval would still be a few years away.
Shingles, and the all-too-common complication of post-herpetic neuralgia, can be such debilitating conditions that a new, more effective vaccine would be a very welcome addition. It could help prevent more cases of shingles in older adults. And since HZ/su can’t cause infection, it could be given to people with weakened immune systems.