Shingles, also known as herpes zoster, is a viral infection that results in a painful rash. This condition is caused by the same virus responsible for chickenpox, the varicella-zoster virus (VZV). While not typically life-threatening, shingles can be very painful and lead to complications.
Understanding the Shingles-Chickenpox Connection
The varicella-zoster virus (VZV) causes chickenpox upon initial infection, typically in childhood. After an individual recovers from chickenpox, the VZV does not leave the body. Instead, it becomes inactive and remains dormant in nerve cells for life.
Years or even decades later, this dormant virus can reactivate, traveling along nerve pathways to the skin and causing the painful rash of shingles. This reactivation is often linked to a decline in the immune system’s ability to keep the virus suppressed, which commonly occurs with aging. Shingles is therefore a re-emergence of this latent virus, not a new infection.
Why Past Chickenpox Exposure Matters
Shingles can only develop in individuals who have previously been infected with VZV, meaning a past chickenpox infection is a prerequisite. Many adults in the United States, especially those born before 1980, were exposed to VZV and had chickenpox as children.
In many instances, chickenpox infections were mild or occurred at a very young age, making them difficult to recall. Over 99% of Americans aged 40 and older have evidence of past VZV infection, regardless of whether they remember having chickenpox. While serological testing can confirm prior VZV exposure, it is generally not necessary when considering shingles vaccination.
The Shingles Vaccine: Its Purpose and Protection
The currently recommended shingles vaccine, Shingrix, is a non-live, recombinant vaccine. It contains a specific protein from the varicella-zoster virus called glycoprotein E, combined with an adjuvant system. This design helps to induce a strong immune response in vaccinated individuals.
The vaccine works by boosting the body’s immune system to target the VZV. This enhanced immune response helps to prevent the dormant virus from reactivating and causing shingles. Shingrix is highly effective, demonstrating over 90% efficacy in preventing shingles and significantly reducing the risk of post-herpetic neuralgia (PHN), a long-term nerve pain complication that can follow a shingles rash.
Current Vaccine Recommendations
The Advisory Committee on Immunization Practices (ACIP) and the Centers for Disease Control and Prevention (CDC) recommend the shingles vaccine for healthy adults aged 50 and older. This recommendation applies irrespective of whether they recall having had chickenpox or not.
The Shingrix vaccine is administered as a two-dose series. The second dose is typically given between 2 and 6 months after the first dose. Completing both doses provides the full intended protection against shingles and its associated complications.