Older people get shingles because their immune systems gradually lose the ability to keep a dormant virus in check. The virus responsible, varicella-zoster, is the same one that causes chickenpox. After a childhood infection, it never actually leaves the body. It hides in nerve cells for decades, held in place by immune defenses that weaken with age. About 1 in 3 people in the United States will develop shingles in their lifetime, and the risk climbs sharply after age 50.
Where the Virus Hides for Decades
When you recover from chickenpox as a child, the virus travels along sensory nerve fibers from the skin into clusters of nerve cells called ganglia. These ganglia sit along the spinal cord and near the base of the skull, running the full length of the nervous system. The virus essentially goes to sleep there, remaining inactive but alive inside neurons for the rest of your life.
Because the virus is stored in ganglia along the entire spine and skull, shingles can appear anywhere on the body when it reactivates. The virus travels back down the nerve fibers to the skin, which is why a shingles outbreak typically shows up as a band or strip of blisters on one side of the body, following the path of a single nerve.
How Aging Weakens Virus Control
Your immune system doesn’t just fight off new infections. It also runs constant surveillance on threats already inside your body, including dormant viruses. A specific type of white blood cell is responsible for recognizing and destroying cells that harbor varicella-zoster. As long as these immune cells remain active and plentiful, they suppress the virus and prevent it from replicating.
With age, the immune system undergoes a process called immunosenescence, a gradual decline in its ability to function effectively. The cells responsible for keeping varicella-zoster in check become less numerous and less effective at recognizing the virus. This decline doesn’t happen overnight. It’s a slow erosion over decades, which is why shingles risk rises steadily after 50 rather than appearing suddenly at a particular birthday. By age 60, the immune system’s virus-clearing ability has often weakened enough to give the dormant virus an opening to reactivate.
Other Triggers Beyond Age
Age is the biggest risk factor, but it’s not the only one. Anything that further suppresses the immune system can tip the balance and allow the virus to wake up. People who have had organ transplants, those undergoing cancer treatment (particularly for leukemia or lymphoma), and those living with HIV face a significantly higher risk. Long-term use of immunosuppressive medications, including steroids, also increases vulnerability.
Physical and emotional stress may play a role as well, though the connection is harder to quantify. What’s clear is that the underlying mechanism is always the same: when immune surveillance drops below the threshold needed to contain the virus, reactivation becomes possible.
What Shingles Feels Like
Shingles typically announces itself with pain before any rash appears. This prodromal phase usually lasts three to five days and can include burning, tingling, or a deep ache in one area of the body. In older adults, this early pain is sometimes mistaken for other conditions. One documented case involved a 70-year-old man whose leg pain was initially evaluated as a spinal problem before shingles was identified. The pain can feel dull and heavy, with occasional sharp sensations, and it tends to follow the path of a single nerve.
After the prodromal phase, the characteristic rash emerges: clusters of fluid-filled blisters on one side of the body. The blisters typically crust over within 7 to 10 days. Some people also experience heightened skin sensitivity in the affected area, where even light touch or clothing feels painful.
Why Complications Hit Older Adults Harder
The most feared complication of shingles is postherpetic neuralgia, chronic nerve pain that persists long after the rash has healed. Among people over 50, roughly 10 to 20% develop this lingering pain, which is defined as pain lasting at least three months after the rash resolves. In a large U.S. study of adults 60 and older, 12.4% developed postherpetic neuralgia, and 41% of those cases continued for at least six months. Some people still report pain a full year later, and in rare cases, the pain lasts for years.
The pain can be constant, intermittent, or triggered by stimulation that wouldn’t normally hurt, like a breeze across the skin. For older adults, this chronic pain can significantly affect daily functioning, sleep, and quality of life. The older you are when you get shingles, the more likely you are to develop postherpetic neuralgia, which is one more reason the disease disproportionately burdens seniors.
The 72-Hour Treatment Window
Antiviral medications can reduce the severity of a shingles outbreak, but timing matters enormously. Treatment is most effective when started within 72 hours of the rash appearing, and some evidence suggests that starting within 48 hours produces the best results. The standard course lasts 7 to 10 days.
Starting antivirals within this window can shorten the duration of the outbreak and reduce acute pain. However, even with prompt treatment, there’s still a risk of developing postherpetic neuralgia afterward. This is part of why prevention through vaccination is considered far more effective than treating an outbreak after it starts.
How Well the Vaccine Works in Older Adults
The current shingles vaccine (Shingrix) is remarkably effective, even in the age groups most vulnerable to the disease. In clinical trials published in the New England Journal of Medicine, the vaccine prevented shingles in about 90% of adults aged 70 to 79, and the protection was nearly identical, 89.1%, in adults 80 and older. It also reduced the risk of postherpetic neuralgia by about 89% in people over 70.
This is a significant improvement over the previous vaccine (Zostavax, no longer available in the U.S.), which lost effectiveness as patients aged. Shingrix maintains its protective effect across older age groups precisely because it uses a different approach to stimulating immunity, one that works even against the backdrop of an aging immune system.
The CDC recommends two doses of Shingrix, spaced 2 to 6 months apart, for all adults 50 and older. This applies regardless of whether you’ve had shingles before or received the older vaccine. If more than six months pass between doses, you don’t need to restart the series. You just get the second dose as soon as possible.