Varicella-Zoster Virus (VZV) is the single infectious agent responsible for both chickenpox (the primary infection) and shingles (the reactivation of the virus decades later). The introduction of the childhood Varicella vaccine complicated the relationship between the two illnesses, creating a distinction between immunity derived from natural infection and immunity from vaccination. It is important to separate the function of the Varicella (chickenpox) vaccine, given to children, from the dedicated Zoster (shingles) vaccine, administered to adults.
The Connection Between Chickenpox and Shingles
Chickenpox, or varicella, is the initial illness that occurs when a person is first exposed to VZV. The virus causes a widespread, itchy, blistering rash before the body’s immune system clears the active infection. VZV does not entirely leave the body; it exhibits latency, a characteristic common among herpesviruses.
The virus travels from the skin lesions to the nervous system, establishing a dormant state within the sensory nerve structures called the dorsal root ganglia. Shingles, medically termed herpes zoster, occurs when this latent VZV reactivates, typically due to a decline in the body’s specific immunity, which happens with age. The reactivated virus travels down the nerve fibers to the skin, causing a painful, localized rash, often accompanied by long-lasting nerve pain known as postherpetic neuralgia.
Impact of the Childhood Varicella Vaccine on Shingles Rates
The childhood Varicella vaccine, a live-attenuated (weakened) virus vaccine, significantly reduces the risk of developing chickenpox. By preventing the initial VZV infection, the vaccine also reduces the likelihood of the virus establishing a robust, reactivatable latent infection. Studies have shown that the incidence of shingles in vaccinated children is substantially lower—around 78% less—than in children who were unvaccinated.
The mass vaccination program has also resulted in an overall decline in pediatric shingles cases, with one large study noting a 72% reduction in the rate of pediatric herpes zoster following the vaccine’s introduction. However, the weakened vaccine strain of VZV can still establish latency, meaning vaccinated individuals are not entirely immune to developing shingles later in life, although the risk is much lower than after a natural infection. Receiving the recommended two doses of the Varicella vaccine offers greater protection against both chickenpox and subsequent shingles compared to a single dose.
The Dedicated Shingles Vaccine
The primary tool for shingles prevention in adults is the dedicated Zoster vaccine, designed to boost immunity against the dormant VZV already present in the body. The most current version of this vaccine, Shingrix, is a non-live, recombinant vaccine that contains a specific viral protein called glycoprotein E (gE), along with an adjuvant to enhance the immune response.
This formulation stimulates the immune system to produce a strong and sustained level of antibodies and T-cells, which are necessary to keep the latent virus suppressed and prevent it from reactivating. Clinical trials have demonstrated high efficacy rates for Shingrix, offering over 90% protection against shingles. This dedicated vaccine is recommended for people who have had chickenpox or the childhood Varicella vaccine decades prior, as their VZV-specific immunity has naturally declined over time.
Summary of Vaccination Recommendations
The Varicella and Zoster vaccines serve distinct purposes and are recommended for different age groups. Children should receive the Varicella vaccine, typically given in a two-dose schedule, with the first dose administered between 12 and 15 months of age.
The Zoster vaccine, Shingrix, is recommended for all healthy adults aged 50 and older, regardless of whether they recall having chickenpox or received the childhood Varicella vaccine. It is administered as a two-dose series, separated by two to six months. Adults aged 19 and older who are or will be immunocompromised due to disease or therapy are also recommended to receive the two-dose Shingrix vaccine.