Shingles (Herpes Zoster) is a viral infection causing a painful rash, typically presenting as a stripe of blisters on one side of the body. It is caused by the varicella-zoster virus (VZV), the same virus responsible for chickenpox. The question of whether to get the shingles vaccine, especially for those who do not recall having had chickenpox, is common. Understanding the biological relationship between the two diseases is necessary to realize the vaccine’s purpose.
The Relationship Between Chickenpox and Shingles
Initial infection with VZV causes chickenpox. After the symptoms resolve, the virus enters a dormant, or latent, state instead of leaving the body. During this latency period, VZV travels along nerve pathways and settles within sensory nerve structures called ganglia. The virus can remain inactive in these nerve cells for decades.
Shingles occurs when latent VZV reactivates, often due to a decline in the body’s virus-specific cellular immunity. This decline is associated with increasing age, as the immune system naturally weakens over time. The reactivated virus travels down the nerve fibers to the skin, causing the characteristic painful rash along the nerve’s path. Shingles can only occur in individuals previously infected with VZV, regardless of whether they remember the initial chickenpox infection.
Who Should Receive the Shingles Vaccine
Public health organizations, such as the Centers for Disease Control and Prevention (CDC), provide guidelines for who should receive the shingles vaccine. The recombinant zoster vaccine (RZV), known as Shingrix, is recommended for all immunocompetent adults aged 50 and older. The recommendation is based on the fact that the risk and severity of shingles and its complications increase significantly with age, with rates increasing substantially between the ages of 50–59 and 70–79.
The vaccine is also recommended for adults aged 19 and older who are immunodeficient or immunosuppressed due to disease or therapy. These individuals are at a higher risk of developing shingles because their weakened immune systems are less able to suppress VZV. There is no upper age limit for receiving the vaccine, and the recommendation applies regardless of whether the person recalls having had chickenpox or a prior episode of shingles.
The Case for Vaccination Without Prior Chickenpox
The most direct answer to the question of vaccination without a history of chickenpox is that the vaccine is still necessary and recommended. For adults in the eligible age group, screening for a prior chickenpox infection is not required before administering the shingles vaccine. This is because the vast majority of adults born before 1980 have been infected with VZV, even if they have no memory of the illness.
Chickenpox infection is highly contagious, and it was nearly universal before the introduction of the chickenpox vaccine. Many people experienced a subclinical infection, meaning they contracted the virus but had such mild or non-specific symptoms that they never realized they had chickenpox. Even a mild or asymptomatic case is enough for the VZV to establish latency in the nervous system. Therefore, if a person is 50 or older, it is safely assumed they harbor the dormant virus capable of reactivating as shingles. The vaccine’s purpose is to boost the immune system’s defense against this silent, latent virus, preventing its future reactivation.
Shingrix Dosage and Effectiveness
The currently recommended vaccine is Shingrix, a recombinant zoster vaccine. It is administered as a two-dose series. For immunocompetent adults, the second dose should be given intramuscularly between two and six months after the first dose. Receiving both doses is important, as the full regimen provides the highest level of protection.
Clinical trials demonstrate that Shingrix offers high efficacy against shingles and its most common complication, post-herpetic neuralgia (PHN). In adults aged 50 to 69, the vaccine is approximately 97% effective at preventing shingles. For adults aged 70 and older, efficacy remains high, at about 91%. Following vaccination, some people experience common, short-term side effects such as pain, redness, or swelling at the injection site, or general symptoms like muscle pain and fatigue.