But for some, the virus can reactivate and cause a range of illnesses, from the common cold to a type of cancer.
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Chickenpox and shingles totally should not be the same thing. One is an itchy rash you get in childhood if you weren’t vaccinated. And one is a totally-different-seeming bout of blisters and nerve pain that usually happens decades later in life. Yet both are caused not just by the same virus, but by the same incidence of the same virus. That’s because chickenpox is caused by one of a group of viruses who excel at making themselves into unwelcome guests… for life. But this particular virus has an even weirder way of doing things. Let’s take a look at how it pulls off this annoying double feature. For some people, particularly those with weakened immune systems, the varicella-zoster virus (VZV) that causes chickenpox can reactivate and cause shingles. Though the exact mechanism is unknown, VZV is thought to enter the body through the respiratory tract and infect T cells of the immune system. It then spreads to the skin, causing itchy, fluid-filled blisters. At the same time, the virus also enters the peripheral nervous system and enters a state of latency, where it remains dormant for decades. To remain in this state, VZV switches on one of its genes, ORF63, which protects human neurons from apoptosis. It also uses ORF61 to maintain latency, by increasing the production of mRNA from those genes. ORF61 is also read in reverse, which prevents it from being made into a protein and keeps the virus hidden from the immune system. In about one third of adults, the virus reactivates and causes shingles, with painful lesions in the areas of skin the neurons connect to. EBV, on the other hand, infects and remains dormant in the same immune cells throughout its life, coming back around as a fresh case of mono. We still don’t know exactly why and how VZV decides to make an unwelcome reappearance, but the fact that it is more likely to occur in the elderly gives us an indication. The decline of the immune system with age may provide the perfect opportunity for VZV to spread more effectively than it did the first time, due to a weakened defence system. This is why the Centers for Disease Control and Prevention (CDC) recommend the shingles vaccine for people aged 50 or over, or those who are immunocompromised.
Though the same virus causes chickenpox and shingles, the two vaccines are different. The chickenpox vaccine contains a weakened form of VZV, whilst the shingles vaccine, Shingrix, contains a single protein found on the surface of the virus. This means that it can be administered to those with weakened immune systems, but still provides enough information for the body to know what to attack if VZV appears again.
There is also another shingles vaccine, which is a live, weakened version of the virus. However, for safety reasons, they are kept separate as they were tested on different groups of patients.
Ultimately, the vaccines work in a similar way, and it appears that those who have had the chickenpox vaccine are less likely to get shingles. As the first large group of people to receive the chickenpox vaccine did so in 1995, they are still relatively young, so this is something that will take some time to understand.
The protection of a vaccine decreases the likelihood of VZV reappearing as a different illness. Although not everyone who has had chickenpox will get shingles, it is still possible; as long as the virus is present, it could come back. Herpesviruses are like that last guest at a dinner party who refuses to leave, even after being asked nicely, and just hides out until they find the right moment to make an unwelcome return.
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