The question of whether a person vaccinated against chickenpox can still develop shingles is common. The answer is yes, shingles is possible even after vaccination, because both conditions are caused by the same organism, the Varicella-Zoster Virus (VZV). Chickenpox, or varicella, is the initial infection from VZV, while shingles, or herpes zoster, represents the virus reactivating later in life. This fact means that any exposure to VZV, whether through a natural infection or a vaccine, can potentially lead to shingles.
How the Virus Causes Shingles
The Varicella-Zoster Virus belongs to the herpesvirus family, known for its ability to establish a latent state within the host’s body. After the initial chickenpox infection clears, VZV travels along nerve fibers and takes up permanent residence in the sensory nerve ganglia near the spinal cord and brain. In this latent state, VZV is mostly silent for decades.
Shingles occurs when the immune system’s ability to keep the virus in check weakens, often due to aging, stress, or illness. This decrease in cell-mediated immunity allows the dormant virus to reactivate and multiply. The active virus then travels back down the nerve pathway to the skin, causing the characteristic, painful, blistering rash of shingles, which typically appears on only one side of the body.
How the Chickenpox Vaccine Affects Shingles Risk
The varicella vaccine uses a live, weakened (attenuated) strain of VZV. Because the vaccine introduces the virus, it can still establish latency in the sensory nerve ganglia, meaning shingles is possible in vaccinated individuals. However, the risk of developing shingles is significantly lower after vaccination compared to having a natural chickenpox infection.
Studies show that children who received the chickenpox vaccine have a 78% lower incidence of shingles compared to unvaccinated children. For instance, vaccinated children experienced shingles at a rate of 38 per 100,000 person-years, while the rate for unvaccinated children was 170 per 100,000 person-years. When shingles occurs in a vaccinated person, it is often referred to as “breakthrough zoster.” The resulting disease tends to be milder, shorter in duration, and less likely to lead to severe complications like postherpetic neuralgia (PHN).
The protection is maximized with the full two-dose series; children who received two doses had a 50% lower risk for shingles compared with those who only received one dose. While the vaccine reduces the likelihood of reactivation, it does not eliminate it completely. This reduced risk is considered a benefit of the varicella vaccine, reinforcing its importance for public health.
The Importance of the Shingles Vaccine
A separate vaccine is recommended later in life to prevent shingles reactivation. The Shingles (Zoster) vaccine is designed to boost the cell-mediated immunity against VZV that naturally declines with age. This boost helps the immune system maintain control over the latent virus, preventing reactivation and the painful rash.
The recombinant zoster vaccine (RZV), currently the only one available in the United States, demonstrates over 90% efficacy in preventing shingles. This vaccine is recommended for all healthy adults aged 50 years and older. It is also recommended for adults aged 19 and older who are at increased risk of shingles due to a compromised immune system.
The recombinant vaccine is given in a two-dose series. Its high efficacy against shingles and complications, such as postherpetic neuralgia (PHN), applies even to those who were vaccinated against chickenpox decades earlier.