Shingles, or herpes zoster, is a painful blistering rash caused by the reactivation of the varicella-zoster virus (VZV), the same virus that causes chickenpox. After recovery from chickenpox, VZV does not leave the body but enters a dormant state. Recurrence is possible, though it is not common for most individuals. While the majority of people experience only one episode, studies suggest that between 1.2% and 9.6% of people who have had shingles will experience a second outbreak.
Understanding Viral Latency
The possibility of shingles recurrence is rooted in viral latency, the unique way VZV interacts with the human nervous system. Following the initial chickenpox infection, VZV particles travel from the skin and mucous membranes to the sensory nerves. The viruses migrate along nerve fibers to the dorsal root ganglia (DRG), clusters of nerve cells located near the spinal cord and brain.
Once inside the DRG neurons, the virus’s genetic material integrates and becomes inactive, entering a state of latency. In this dormant state, the virus is hidden from the immune system and does not replicate, but it is never fully eliminated. The virus may remain in this quiescent state for decades, held in check by the host’s ongoing immune surveillance. This silent presence within the nerve tissue is the biological mechanism that allows for future reactivation.
Factors Triggering Reactivation
Reactivation occurs when the immune system’s ability to monitor and suppress the dormant VZV weakens. The most significant factor compromising immune surveillance is advanced age, which causes a natural decline in cell-mediated immunity over time. This process, known as immunosenescence, explains why shingles is far more common in adults over the age of 50.
A compromised immune system due to underlying health conditions also triggers VZV reactivation. Diseases like HIV, certain cancers (such as leukemia and lymphoma), and chronic conditions like diabetes impair the body’s ability to keep VZV in check. For those with severely weakened immunity, the recurrence rate can climb significantly higher, sometimes reaching up to 18%.
Taking immunosuppressive medications dramatically increases the risk. These include high-dose steroids, chemotherapy drugs, or biologics used for autoimmune diseases. These treatments intentionally suppress the immune response, opening a window for the latent virus to reactivate. Significant physical trauma or chronic emotional stress may also contribute by temporarily taxing the immune system. Once reactivated, the VZV travels back down the nerve fiber to the skin, causing the characteristic painful rash.
Strategies for Reducing Recurrence Risk
The primary strategy for reducing the risk of a recurrent shingles episode is vaccination. The recombinant zoster vaccine, Shingrix, is recommended for all adults aged 50 and older, regardless of whether they have previously had shingles. This non-live vaccine is administered as a two-dose series and works by boosting the immune system’s defense against VZV.
Clinical data shows Shingrix offers high protection, with approximately 97% efficacy in adults aged 50 to 69 and over 90% efficacy in those aged 70 and older. The vaccine is recommended even after a shingles episode because prior infection does not provide guaranteed, long-lasting immunity against recurrence. This high level of protection is maintained for at least a decade following the two-dose series.
Supporting strategies focus on maintaining overall health to manage the latent virus. This includes actively managing chronic conditions like diabetes and autoimmune disorders under a doctor’s care. Practicing stress reduction techniques, ensuring adequate sleep, and maintaining good nutrition also contribute to robust immune function.