A new study claims to have ruled out a link between childhood vaccination against varicella (chickenpox) and the increased incidence of herpes zoster (shingles) in adults, according to an article published in the Annals of Internal Medicine.
Chickenpox and shingles are both caused by the same virus - the varicella zoster virus (VZV). The first exposure to the virus can lead to varicella or chickenpox, which is a common and fairly mild illness. Predominantly a childhood illness, adults can also get it.
Although exposure to the virus or the vaccine means the body will develop antibodies to the infection, which offer immunity from catching it again, the varicella virus has a sting in its tail. This virus remains dormant (inactive) in the body's nerve tissues and can return later in life as shingles.
Shingles is characterized by a painful rash, which develops into clusters of clear vesicles or blisters. These continue to form for between 3 and 5 days before crusting over and drying out.
In most cases, the vesicles will completely heal within 2 to 4 weeks, although they may leave pigmentation changes or scarring on the skin.
According to the Centers for Disease Control and Prevention (CDC), there are an estimated 1 million cases of shingles each year in the US - with almost one in three people contracting it at some point in their lifetime.
Rising rates of shingles
The most prevalent complication some people develop is postherpetic neuralgia (PHN), a severe nerve pain that can last for months or even years after the rash has cleared up. The CDC says that one person in five will experience PHN.
The organization notes that as people get older, the chances of developing PHN increase and the pain is likely to be more severe.
According to the study, herpes zoster incidence is on the rise among adults in the US. The authors acknowledge there is concern that the universal vaccination program of American children has stopped adults from achieving the immunity benefits associated with external exposure to the virus, although this has not been proven.
For the study, the authors reviewed more than 2.8 million Medicare claims from 1992 through 2010 to establish if the vaccination program really is the catalyst to the rising shingles rates in patients over 65 years of age.
The researchers claim that the data shows this age-specific trend in shingles predates 1996 - the year the childhood varicella vaccination program began. They also say there is no variation in the prevalence of herpes zoster incidence between states, even though the vaccination coverage did vary.
Although the authors cannot explain why there is an increase in herpes zoster incidence in older people, they do not believe the varicella vaccination program is connected to it.
Indeed, they go further to suggest the wider use of the vaccination should be used within the American population.