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Why we vaccinate-shingles may increase risk of stroke

Last updated on August 24th, 2019 at 11:18 am

shingles-vaccineThis article, originally published on 2 January 2014 has been updated to include more information about studies regarding chickenpox in children and its effect on rate of shingles outbreaks.

Shingles, known medically as Herpes zoster (HZ), is caused by the Varicella zoster virus (VZV), which causes chickenpox in children. After the chickenpox infection, VZV latently persists, without symptoms, in the basal ganglia including the trigeminal ganglion. For unknown reasons, VZV is reactivated from latency, and moves along sensory nerves to the endings in the skin, where it replicates causing the characteristic HZ rash, commonly called shingles.

There is no known cure for VZV, though it can be treated with antiviral medications. Although the infection presents with a rash, commonly fairly painful, it usually subsides within three to five weeks. Unfortunately, about one in five patients develop a painful condition called postherpetic neuralgia, which is often difficult to manage. Because VZV is never eliminated, after a shingles attack, VZV again becomes latent, to attack again sometime in the future.

There are other more serious complications from HZ. In a recent report in the journal Neurology, the authors examined over 106,000 medical records of patients who have had an HZ attack compared to a control group of over 213,000 patients. They found that for subjects who had HZ before the age of 40, they had 2.42X the risk for stroke and 1.49X the risk for TIA (transient ischemic attack, a transient episode of neurologic dysfunction caused by loss of blood flow without tissue death, almost a milder form of stroke). In older subjects, the differences were smaller because there is better assessment of cardiovascular risks with early intervention.

Of course, VZV infection can be prevented in children with the chickenpox vaccine. Because if you prevent VZV infection, then there is almost a zero risk of HZ. 

Unfortunately, the chickenpox vaccine did not become available widely until the early 1990’s, so anyone older than 25 probably contracted chickenpox and is at high risk of eventually developing shingles, putting them at risk for rashes, pain, stroke and other complications. 

Fortunately for those who are at risk for HZ, there is a vaccine that is very effective in preventing the latent VZV from reactivating–a shingles vaccine. According to a recent Cochrane systematic review, “Herpes zoster vaccine is effective in preventing herpes zoster disease. In general, zoster vaccine is well tolerated; it produces few systemic adverse events and injection site adverse effects of mild to moderate intensity.” So until we eliminate chickenpox with its vaccine, we can prevent reactivation of the varicella virus by another vaccine (which admittedly is just the adult dose of the chickenpox vaccine).

Now there is a trope pushed by vaccine deniers–exposure to the children getting chickenpox acts as a booster that causes the adult immune system to block VZV reactivation. I am personally flabbergasted by such a belief, if it were true. They want children to get chickenpox to act as a “vaccine” for older individuals? Given the significant complications of chickenpox (secondary infections, brain and neurological complications, scarring, and other serious issues), these antivaccinationists want us to put children at risk of disease to protect others, when there’s a perfectly safe protection against shingles–a vaccine.

Moreover, there is little evidence that increased chickenpox vaccination of children leads to higher rates of shingles in adults. In a recent article in the Annals of Internal Medicine, study author Dr. Craig Hales, a medical epidemiologist at the U.S. Centers for Disease Control and Prevention (CDC), examined Medicare (the US Federal insurance system for disabled and elderly individuals) claims data from 1992 to 2010 that included about 2.8 million people over the age of 65.

Hales found that annual rates of shingles increased 39 percent over the 18-year study period, which might make one conclude that the suppression of chickenpox outbreaks lead to a large increase in shingles. However, the researchers failed to find a statistically significant change in the rate after the introduction of the chickenpox vaccine–in other words, the rate of shingles seems to be increasing regardless of chickenpox vaccinations. Furthermore, the researchers hypothesized that the rate of shingles would be lower in states with lower chickenpox vaccination uptake, but they, in fact, determined that the rate of shingles didn’t vary from state to state where there were different rates of chickenpox vaccine coverage.

It is possible that some other cause is associated with the increase in shingles. For example, immune suppression, as a result of stress, can lead to HZ activation in at risk individuals. Despite claims of a very biased antivaccination computer scientist (who lacks any medical and epidemiology background) that, in one small area of Los Angeles County, increased chickenpox vaccination lead to increased shingles rates, the study only showed correlation, and failed to show any causation. This is why small primary studies should be examined critically, and large multi-site studies, like Hales’ examination of 2.8 million people, have much more credibility and lead science in the right direction–there is some other, as of yet, unknown causality to the increase in HZ.

So, get children vaccinated against chickenpox. It is dangerous to believe that we should allow children to get chickenpox, which has a small but statistically significant risk of serious complications, just to support the debunked myth that wild-type VZV prevents shingles. We know how to prevent shingles–vaccinating children so that they never are at risk of HZ. And vaccinating adults to prevent HZ from activating in adults who had chickenpox.

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Michael Simpson

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