Large study finds no link between COVID vaccine and shingles


I didn’t know it was a thing, but I guess some people claimed that there was a link between a COVID-19 vaccine and shingles. But in the name of science, researchers published a study that refuted the link between the COVID-19 vaccine and shingles.

I’m glad it’s not linked, even though I never thought it was. So, as I always do, let’s review the study and see what it says.

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Photo by Nataliya Vaitkevich on Pexels.com

What is chickenpox? Shingles?

One of the consequences of contracting chickenpox, a virus called Varicella zoster, is that the virus is not destroyed by the body’s immune system. Once the symptoms of chickenpox disappear, the virus hides (it does not do this consciously, it’s a virus) in the dorsal root ganglion, a bundle of nerve fibers at the bottom of the spinal column. The virus just hangs out there, basically hidden from the body’s immune system.

We are not sure why it does this, but it may be an evolutionary adaptation to survive until a later point in time so that it can reproduce and reinfect the victim. Of course, viruses are very simple organisms (and some biologists will debate that they are not living organisms), so complex behavior may be pushing our understanding of a virus.

Even though the body generated an immune response to the original zoster virus infection, several years or decades after the initial infection, the adaptive immune response wanes, weakens or disappears. Due to other unknown factors, possibly stress or other infections, the zoster virus “moves” (again, it’s a virus, so it just multiplies without purpose) along the nerve bundles, and causes the second infection with much more serious consequences to the patient.

This second infection is called herpes zoster, more commonly known as shingles. This infection usually happens when the patient is older than 50, although it can happen at any time, occasionally even in young adults. 

What can be said about shingles is that it’s an entirely unpredictable disease. It really appears at random points in time in response to unknown variables. Once shingles appear, it is incredibly painful, depending on the location of the outbreak. It can cause blindness, disfigurement of the area infected, permanent pain, and other conditions.

Shingles can be treated with antiviral drugs, but only if the infection is recognized and treated within 24-72 hours, a time frame that might not allow most individuals to get to their doctor. The initial symptoms may even appear like acne or some other skin condition, which many people might ignore. After 72 hours, the disease has to run its painful and dangerous course. The pain of shingles may last for weeks, months, or even years after the blisters have healed – this is not a trivial disease.

The only way to prevent a shingles infection is to boost the immune system with a new vaccine against the zoster virus. Zostavax (a shingles vaccine available in the USA) has been approved by the FDA for the prevention of shingles in 50-59-year-olds (and it has previously been approved for 60-69-year-olds).  If I had contracted chickenpox, I’d ask for the vaccine even in my 40s, just to prevent the more serious shingles outbreak. But that’s not medical advice.

So let’s be clear about a couple of things. First, you are only at risk for shingles if you contracted chickenpox. Second, children who have been vaccinated against chickenpox probably will never, ever contract shingles. Is this clear? The chickenpox vaccine prevents chickenpox AND shingles later in life.

COVID-19 vaccine and shingles study

In an article published on 1 November 2022 in JAMA Network Open, Nisha Acharya, MD, MS, of the University of California San Francisco, and colleagues examined whether there was a link between a COVID-19 vaccine and shingles in a database study that included more than 2 million individuals in the US.

A total of 2,039,854 individuals who received any dose of a COVID-19 vaccine with emergency use authorization (Pfizer, Moderna, and JNJ vaccines) from December 11, 2020, through June 30, 2021, were eligible for inclusion.

These are their key results:

  • The risk of herpes zoster in the month after receiving a dose of the COVID-19 vaccine was no different when compared with a control period of 60 to 90 days following an individual’s last dose, incidence rate ratio (IRR) = 0.91.
  • When compared with influenza vaccination during a period before the pandemic, COVID-19 vaccination was associated with a slightly lower shingles risk.
  • There was no risk for people aged 50 and over IRR=0.90.

Of course, there is an actual risk of shingles as a result of COVID-19 infection itself. That is one, of many, reason to get the COVID-19 vaccine.

This study contradicts two previous studies that seem to indicate a link between COVID-19 vaccines and herpes zoster. An international matched cohort study involving more than 1 million COVID-19-vaccinated individuals detected a nearly two-fold higher risk of shingles within 60 days of COVID-19 vaccination. And a large case-control study from Israel that involved over 880,000 vaccinated individuals and an equal number of comparators reported a 43% higher risk of herpes zoster after vaccination.

One reason that this study might differ from the other two is that the US study was much more demographically diverse. There might be some confounders in the other studies that made it appear that there was a higher risk of herpes zoster after COVID-19 vaccination.

This is how science progresses, more data and evidence are uncovered that either supports or dismisses concerns about vaccines. This new study clearly dismisses any link between the COVID-19 vaccines and shingles. One of the strengths of the new study is that the number of individuals was extremely large — over two million.

I think that for now, the link between COVID-19 vaccines and shingles is very tenuous if nonexistent.

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