Shingles, also known as herpes zoster, is a painful rash caused by the reactivation of the Varicella-Zoster Virus (VZV), which first causes chickenpox. While most people only experience one episode, the virus remains permanently in the body, meaning it can reactivate again. Understanding the underlying biology and preventative measures is important because recurrence is possible.
The Biology of Viral Latency
The underlying reason for shingles recurrence is viral latency. After recovering from chickenpox, VZV travels along nerve fibers and establishes a dormant state within the sensory nerve ganglia (clusters of nerve cells near the spinal cord). The virus remains inactive for years while the immune system keeps it suppressed.
Reactivation occurs when the body’s T-cell immunity declines, allowing the dormant VZV to multiply and travel back to the skin. This causes the characteristic painful, blistering rash of shingles, typically confined to the area served by the affected nerve. Since a new episode is a reactivation of the existing virus, it can happen multiple times if immune control wanes.
Statistical Likelihood of Recurrence
Although recurrence is possible, most people who have had shingles will not experience a second episode. Studies suggest that approximately 1.2% to 9.6% of the general population will have a recurrence. This rate is significantly higher for immunocompromised individuals, potentially reaching up to 18%.
The likelihood of a second episode increases over time following the initial bout. The cumulative incidence of recurrence was found to be 2.5% at two years and 10.3% at ten years after the first episode. The average time interval between episodes is typically three years or more for adults over 55. Recurrence is lowest in the first year following an episode due to the temporary boost in immunity.
Key Factors Increasing Recurrence Risk
The risk of recurrent shingles is strongly linked to the status of T-cell immunity, the main defense against VZV reactivation. Advanced age is a major factor because T-cell function naturally declines, increasing susceptibility. People over 50 are generally at higher risk, and this risk continues to climb with each passing decade.
Overall health status and certain medical treatments can also significantly weaken the immune response. Immunocompromised states, such as those caused by HIV, cancer treatments, or organ transplantation, dramatically raise the probability of recurrence. Chronic conditions, including autoimmune diseases, diabetes, and cardiovascular risk factors like dyslipidemia and hypertension, are also identified risk factors. Prolonged zoster-related pain (lasting longer than 30 days after the initial episode) is also associated with an increased risk of a second bout.
Preventing Future Shingles Episodes
The most effective strategy for preventing future episodes of shingles is vaccination. The recombinant zoster vaccine, Shingrix, is recommended for adults aged 50 and older, including those who have already had a shingles episode. This two-dose vaccine creates a strong immune response to keep the VZV latent.
Clinical trials show the vaccine is highly effective, with approximately 97% efficacy in adults 50 and older and about 90% efficacy in those 70 and older. This high level of protection is maintained for many years and is effective for those who are immunocompromised. While vaccination is the primary defense, supporting general immune health through adequate sleep, a balanced diet, and managing chronic stress may also help maintain immune system strength.