How Good Is the Shingrix Vaccine Against Shingles…or Dementia?

If you have ever had chicken pox as a kid, you are at risk for shingles as an adult. That’s because the virus that causes this childhood illness is varicella zoster, the same virus that causes shingles. Even though we get over chicken pox, the virus remains in our bodies. It migrates up nerve cells to the trigeminal and dorsal root ganglia near the brain and spinal cord. The virus goes dormant for decades and can reemerge when our immune system lets down its guard. This can happen as we age or after immune suppressing drugs. The key question: how effective is the Shingrix vaccine in preventing a shingles attack? That’s what this reader wants to know.

Shingles Suffering Can Be Horrific!

Q. My older brother suffered from long-lasting pain after shingles. This is something my late mother experienced as well. Consequently, I decided to go ahead and get the Shingrix vaccine.

For most people, it seems, the side effects of the vaccine are likely to be less troubling than the suffering resulting from shingles. My wife and I both had the vaccine. We had sore arms, with warmth at the injection site, but that was it. My brother is still receiving care at a pain-control clinic several years after having shingles. I would like to avoid that fate!

How Good is the Shingrix Vaccine Really?

A. The Centers for Disease Control and Prevention estimate that the Shingrix vaccine is about 97 percent effective in people 50 to 69 years old. Effectiveness drops a bit in people over 70, to about 91 percent. That’s still impressive.

Protection remains high for at least four years after vaccination. That’s also impressive.

Postherpetic Neuralgia:

Shingles is a painful rash caused by the virus that causes chickenpox. Sometimes after the rash fades, the patient is left with excruciating nerve pain and tenderness in that area of the skin. That complication is called postherpetic neuralgia.

It can be extremely hard to treat. Two doses of the Shingrix vaccine were 86 percent effective in preventing the development of postherpetic neuralgia, the lasting pain your brother has suffered.

Teresa describes her challenges with postherpetic neuralgia:

“I have had shingles on the top of my head, my forehead and inside my eye and it’s been a year, 4 months and 3 days. It still feels like I have a hole on the top of my head. My face has a constant tremor. My eye has an infection in it now called keratitis with postherpetic neuralgia.

It burns with constant, sharp, knife-like pain that goes down through my head and behind my eye. I have tremors all over my body. I have been taking Benadryl and Lortab (hydrocodone and acetaminophen) 4 times a day.  It helps, but not much.  I can’t keep doing this. I have about had it. I can’t sleep.”

Can You Get Shingles More Than Once?

Q. I had a bad case of chickenpox when I was a kid. When I was in my 60s, I had shingles.

I have read that the Shingrix vaccine is very effective. Since I have already had shingles, do I need this vaccine?

A. According to the CDC, people can get shingles more than once. The agency urges everyone over 50 to get two doses of the Shingrix vaccine even if they have had a previous outbreak. The immunization can protect against complications such as long-lasting nerve pain (postherpetic neuralgia) that may follow a shingles attack.

A study suggests that the varicella zoster virus that causes shingles can reactivate the herpes virus responsible for cold sores (Journal of Alzheimer’s Disease, Aug. 2, 2022). Vaccination against shingles may reduce the risk for this worrisome chain of events. That is important because reactivation could be a risk factor for Alzheimer’s disease, so immunization might reduce the likelihood of developing dementia.

Shingles Vaccines vs. Dementia:

Vaccines seem like an improbable way to reduce the risk of developing dementia. And yet the research has been accumulating to support just such a strategy.

A bureaucratic quirk in the roll out of the first shingles vaccine in Wales created a research opportunity. Previous studies had suggested that people who got vaccinated were less likely to develop dementia than those who did not. There could be many reasons for that, however. In such observational studies, there is no good way to make sure that both vaccinated and unvaccinated groups are similar in all other ways.

That is why the decision of the Welsh government to start shingles vaccinations on September 1, 2013, was so useful. Older people who were born on or after September 2, 1933, were eligible, whereas those who had already turned 80 were not. The researchers took advantage of this situation and analyzed detailed electronic health records. The idea is that people a year older and those a year younger would be similar in all other ways, except for being eligible for vaccination against shingles.

The same kind of situation occurred in Australia a few years later. People between 70 and 79 years old got free shingles vaccines, but those who had turned 80 before November 1, 2016, did not have access to the vaccination.

The results in both countries were strikingly similar. Those whose birthdays disqualified them from the vaccine were more likely in the next several years to be diagnosed with dementia (Nature, April 2, 2025; JAMA, April 23, 2025).

The Vaccine Mechanism of Action vs. Dementia:

Why would a shingles vaccine have any impact on the development of dementia? The authors of the most recent study suggest several potential explanations. When the chickenpox virus (varicella zoster) that causes shingles is reactivated, the brain may respond with inflammation and damage to the small blood vessels that nourish it. At the same time, there may be microbleeds, blood clots or vessel blockage.

These insults could trigger the cascade of events that leads to amyloid buildup in the brain. The virus that causes a shingles outbreak may also reactivate other herpes viruses such as those that cause cold sores. These viruses could cause a lot of damage in the central nervous system.

Interestingly, this theory is not new. More than 40 years ago, a pathologist named Melvyn J. Ball, MD, suggested that Alzheimer disease might be in part triggered by herpes virus infections (Canadian Journal of Neurological Sciences, Aug. 1982).

Shingrix Vaccine vs. Dementia

The recent studies from Wales and Australia involved an older shingles vaccine called Zostavax. This vaccine has since been replaced by a more effective immunization called Shingrix that was approved by the FDA in 2017. There is evidence that people who get the recommended series of two Shingrix shots may have an even better chance of escaping dementia (Nature Medicine, Oct. 2024).

Comparing Shingrix to Zostavax:

Before Shingrix, doctors offered shingles prevention with the Zostavax vaccine. It is not as effective as Shingrix, and the protection fades after four or five years. Shingrix does not seem to suffer from that drawback. Still, many readers wonder about the differences between the two vaccines, as this one does.

Q. I had a shingles vaccine about six years ago, but I did have a mild outbreak of shingles several months ago. I’m seeing ads on television for Shingrix. How effective is this newer vaccine for preventing outbreaks?

A. The trial data for Shingrix shows a relative risk reduction of 97 percent. Research indicates that for every eleven people getting vaccinated, one would be spared a shingles outbreak. This is considered a very favorable result. To prevent a single longer-lasting painful episode of postherpetic neuralgia, 34 people would need to get the shot (Applied Health Economics and Health Policy, June 28, 2019).

The Two-Shot Shingrix Vaccine Dilemma!

Shingrix is given as two shots two to six months apart. After its introduction in 2017, the vaccine was in short supply, so many people who wanted to receive it had trouble finding it.

We received a number of complaints from people who got the first Shingrix vaccine but then discovered they could not get the follow-up injection.

Dr. William Schaffner is one of the country’s leading vaccine experts. He is professor of preventive medicine and infectious disease at Vanderbilt School of Medicine.

In an article for Consumer Reports, Dr. Schaffner stated:

“The CDC’s recommendation, based on evidence from clinical trials, is to get your second dose of Shingrix anywhere from two to six months after the first.

“But if it takes longer than that to locate a second dose, don’t worry, Schaffner says. The CDC advises simply getting that second dose as soon as you can find it—and no, you don’t have to start the series over.

“’The timing is not critical,’ Schaffner notes. ‘You just don’t want to get it sooner than recommended because then the body’s immunity is still working on the first dose, so you don’t get the full benefit of the second.’”

As of this writing, there is no longer such a shortage of the Shingrix vaccine. During the pandemic, fewer people have made routine doctor visits or gotten routine vaccinations. In addition, GSK continued production. As a result, the supply has been replenished. When the COVID-19 pandemic ends, however, the company may once again find it difficut to keep up.

Individuals who received the older shingles vaccine, Zostavax, at least five years ago can still benefit from the newer Shingrix vaccine.

One Last Word on a Serious Side Effect:

In 2021, the FDA required the maker of Shingrix, GSK, to change its prescribing information (FDA Safety Communication, March 24. 2021). Postmarketing research showed that people getting Shingrix were slightly more susceptible to a neurological complication called Guillain-Barré syndrome (GBS). The risk meant an addition 6 people per million developed this serious problem in the first month and a half after vaccination.

Read more about Shingrix in this post by our consultant, Karen Berger, Pharma, RPh:

There are 70 comments from other readers following Karen’s article. You may find them of interest.

Perhaps you are still wondering what viruses have to do with dementia and why we have not been discussing amyloid plaques. That, after all, has been the dominant theory of Alzheimer disease for years.

Given the evidence, though, we think it is time to look at the bigger picture. Could amyloid buildup be the brain’s immune reaction to infection? If so, the success of vaccines at reducing the risk of dementia makes sense.

The relatively new anti-amyloid drugs are very expensive. The price of PET scans and ancillary expenses drives the cost up even more. A vaccine is much more affordable. If it reduces the risk of developing dementia even a little bit, it would be well worth the price. And let’s not forget the primary value…preventing a shingles attack!

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