Herpes Zoster Rates Are Increasing, but Why?

Hello. I am Dr. Craig Hales, a physician and epidemiologist at the Centers for Disease Control and Prevention (CDC). I am speaking with you as part of the CDC's Expert Video Commentary series on Medscape.

Herpes zoster rates among adults have been slowly rising over time in the United States and other countries. In the United States, herpes zoster rates have increased by 39% from 1992 to 2010 among adults older than 65 years of age.

Scientists have proposed various hypotheses to explain this increase. A common hypothesis is that the increase in herpes zoster is associated with the widespread vaccination of children against varicella.^[1,2,3,4,5] However, a new CDC study that I will discuss today adds to a growing body of evidence that this is unlikely.

Let's start with some basics. Herpes zoster, also commonly known as zoster or shingles, is a painful skin rash. It is caused by the varicella zoster virus (VZV), which is the same virus that causes varicella disease (chickenpox). After a person recovers from varicella, the virus stays dormant in the sensory ganglia and can reactivate years later, causing zoster.

The reasons why the virus reactivates are not well understood. However, a person's risk for zoster may increase as immunity to VZV declines. This decline in immunity can occur as people get older or if they develop immunodeficiency because of certain medical conditions or medications.

Some scientists have suggested that exposure to varicella disease may boost a person's immunity to VZV and reduce the risk for VZV reactivation as zoster. Some studies have shown reduced risk for zoster in adults who are exposed to varicella, but other studies have not shown this effect.^[6,7,8,9,10]

In the years following implementation of the childhood varicella vaccination program in the United States in 1996, rates of varicella in children fell dramatically. This led some scientists to speculate that increases in zoster in adults were the result of widespread vaccination of children against varicella, because adults have fewer opportunities to be exposed to varicella disease in children. However, this seems increasingly unlikely.

A recent CDC study, using Medicare data from 1992 to 2010, found that among adults aged 65 years or older, zoster rates were increasing even before the varicella vaccine was introduced in the United States.^[1] Moreover, zoster rates didn't accelerate after the routine varicella vaccination program began.

We also examined whether there was a link between state varicella vaccination coverage and zoster rates. Zoster rates did not accelerate as states increased varicella vaccination coverage. In fact, zoster incidence was the same in states with consistently high vaccination coverage as it was in states with lower vaccination coverage.

Our study adds to a growing body of evidence showing that the increase in zoster rates is not a result of childhood varicella vaccination.^[1,2,4,11] CDC continues to study the epidemiology of herpes zoster among adults and children and to monitor the effects of the US varicella and zoster vaccination programs.

Although we still don't know the reasons behind the increases, we do know that many cases of zoster could be prevented by the zoster vaccine. CDC recommends that adults aged 60 years or older receive 1 dose of zoster vaccine to help prevent the disease and its potentially debilitating complications, including post-herpetic neuralgia.

Unfortunately, only 1 in 5 adults aged 60 years or older has received the zoster vaccine. Many opportunities for adult vaccination are being missed. Healthcare professionals can help by strongly recommending zoster vaccine to patients aged 60 years or older and either providing the vaccine or referring patients to providers in the area who can vaccinate.

For more information about zoster and the vaccine, visit CDC's Website

Thank you.

Web Resources

CDC: Shingles (Herpes Zoster)

CDC: Vaccines and Immunizations

CDC: Shingles (Herpes Zoster): Clinical Overview

Craig Hales, MD, MPH, is a preventive medicine physician and epidemiologist in the National Center for Immunization and Respiratory Diseases, Division of Viral Diseases, at the Centers for Disease Control and Prevention in Atlanta, Georgia. Dr. Hales received his MD from Northwestern University and his MPH from the Johns Hopkins University. His current work focuses on surveillance and epidemiology of herpes zoster and herpes zoster vaccine effectiveness and policy.