The rate of shingles has been increasing since the 1990s, and it is now estimated that about one in three adults will develop the disease in their lifetime. A certain number of these people will experience recurring outbreaks. About one in five of them will suffer severe and often debilitating pain known as postherpetic neuralgia (PHN).
Officially, the cause of this increase is unknown. Yet studies suggest that at least part of the explanation could be the chickenpox vaccine.
Chickenpox and shingles are caused by the same virus, which is known as varicella zoster. Shingles cannot occur in someone who has not been previously been infected with the virus, presumably resulting in a chickenpox infection. Why, then, would the vaccine against this virus be causing more severe outbreaks later in life?