The varicella-zoster virus (VZV) is responsible for two distinct diseases: varicella, commonly known as chickenpox, and herpes zoster, also called shingles. Chickenpox is the initial, highly contagious infection, typically occurring in childhood, which causes a widespread, itchy, blister-like rash. Once the body recovers from this primary infection, the VZV does not leave the body but instead goes dormant within the nervous system.
Shingles is the painful rash that results from the reactivation of this latent VZV years or decades later, most often affecting one side of the body. The central question for many who received the childhood chickenpox vaccine is whether that shot truly eliminated the risk of shingles later in life. The short answer is that, while the vaccine offers significant protection, it does not completely prevent the possibility of developing shingles.
The Varicella Vaccine and VZV Reactivation
The varicella vaccine provides immunity using a live, attenuated (weakened) version of the varicella-zoster virus (VZV). This vaccine strain, often called the Oka strain, is intentionally weakened to prevent a full case of chickenpox. The primary purpose of this vaccination is to protect children from complications associated with the wild-type VZV.
Like the naturally acquired wild virus, the live attenuated vaccine strain successfully enters the nervous system and establishes latency. The virus settles primarily in the sensory nerve ganglia, remaining dormant for a lifetime. The presence of VZV genetic material—whether from the wild virus or the vaccine—in the nerve cells creates the potential for future reactivation.
This mechanism means that a person who received the varicella vaccine still harbors the virus in their body, making a future shingles outbreak possible. Reactivation occurs when a person’s cellular immunity to VZV wanes, which typically happens as a person ages or if their immune system becomes compromised. The now-active virus travels down the nerve fibers to the skin, causing the characteristic shingles rash and nerve pain.
The vaccine strain’s ability to reactivate is significantly impaired compared to the wild-type virus, but the risk is not zero. The goal of the varicella vaccine is to prevent severe initial disease while establishing immunity less prone to future reactivation. The presence of the vaccine strain in the body is why vaccinated individuals can still develop shingles.
Comparing Shingles Risk: Vaccination Versus Natural Infection
Although the varicella vaccine does not eliminate the risk of shingles, it substantially reduces the overall incidence compared to natural infection with the wild-type virus. Studies have shown that children who received the chickenpox vaccine have a significantly lower rate of developing shingles later in life. One analysis found that the rate of shingles infection was approximately 78% lower in vaccinated children than in those who contracted chickenpox naturally.
This risk reduction is a major long-term benefit of the childhood vaccination program. When shingles occurs in vaccinated individuals, the disease presentation is typically much milder. The rash is often less extensive, and the acute pain associated with the outbreak tends to be less severe.
A major concern with shingles is postherpetic neuralgia (PHN), which is long-term nerve pain that can persist for months or years after the rash heals. The risk of this debilitating complication is lower in those who received the varicella vaccine. The milder nature of the outbreak suggests the vaccine’s immune memory helps suppress the reactivating virus more effectively.
Preventing Shingles with the Zoster Vaccine
Preventative measures are available for adults to boost declining VZV-specific immunity. The primary method is the zoster vaccine, specifically designed to protect against shingles. The recombinant zoster vaccine, Shingrix, is the preferred option and is recommended for adults aged 50 and older, regardless of their history of chickenpox or varicella vaccination.
This vaccine is administered as a two-dose series, with the second dose given two to six months after the first. The vaccine is highly effective at preventing shingles, demonstrating greater than 90% efficacy in adults 50 years and older. This high level of protection remains strong for several years following the vaccination series.
The Zoster vaccine also provides strong protection against PHN, the most common complication of shingles. By significantly reducing shingles occurrence, the vaccine reduces the chance of developing this chronic nerve pain. Adults who received the chickenpox vaccine should still receive the Zoster vaccine once they reach the recommended age for the highest protection against VZV reactivation.