Shingles vaccine may lower risk of dementia, heart disease

It turns out that the shingles vaccine may have public-health benefits beyond its intended purpose, with new research finding the vaccine appears to lower the risk of dementia as well as heart disease.

Associations have previously been found between herpes virus infections, such as shingles (which also known as herpes zoster or HZ), and an increased risk of developing dementia including Alzheimer’s disease, raising the question of whether vaccination might have a protective effect. However, testing this hypothesis requires large, matched populations of vaccine recipients and control individuals, along with a long follow-up period.

To overcome common bias concerns, Pascal Geldsetzer and colleagues at Stanford University took advantage of a policy in Wales that dictated eligibility for a vaccine against HZ. People born on or after 2 September 1933 were eligible for at least one year for the HZ vaccination from 1 September 2013, whereas those born before this date were not eligible. This policy allowed the authors to compare vaccine-eligible to vaccine-ineligible individuals who differed in their age by merely a few weeks and were, thus, expected to be similar in all characteristics.

The authors used electronic health data to compare new dementia diagnoses between the vaccine-eligible and ineligible population in a cohort of 282,541 individuals born between 1 September 1925 and 1 September 1942. Their results, published in the journal Nature, found that receiving the HZ vaccine reduced the probability of a new dementia diagnosis over a follow-up period of seven years by 3.5 percentage points, corresponding to a 20% relative reduction. This effect was greater in women than in men.

While the authors have proposed potential mechanisms to explain how zoster vaccination might reduce the risk of dementia — such as reduced reactivation of dormant zoster virus or a broader immune mechanism triggered by the vaccine — the study’s observational design means it cannot prove a causal link between vaccination and reduced dementia diagnosis. However, just a few weeks later, Stanford researchers published a similar study in JAMA, this time using Australian data — and it came to a comparable conclusion.

Australians who turned 80 after 1 November 2016 were eligible for a free shingles vaccination, whereas those who turned 80 before this date were not, allowing researchers to compare two groups of people of similar age (although they were unable to confirm actual vaccine receipt, just eligibility). The study of 101,219 patients found that having access to the shingles vaccine decreased the likelihood of receiving a new dementia diagnosis during 7.4 years of follow-up by a statistically significant 1.8%.

It should be noted that both studies were based off the live-attenuated shingles vaccine (Zostavax), rather than the newer, non-live, recombinant vaccine (Shingrix) that is currently used in Australia. Future research will need determine whether Shingrix can provide the same benefit and whether immunisation at younger ages may be just as effective. Nevertheless, the authors of the latter study said that shingles vaccination appears to be a low-cost, high-reward intervention to reduce the burden of dementia.

Finally, a separate study published in the European Heart Journal has found that people who are given a vaccine for shingles have a 23% lower risk of cardiovascular events, including stroke, heart failure and coronary heart disease. The study was led by Professor Dong Keon Yon from the Kyung Hee University College of Medicine.

“Shingles causes a painful rash and can lead to serious complications, especially in older adults and those with weak immune systems,” Yon said.

“In addition to the rash, shingles has been linked to a higher risk of heart problems, so we wanted to find out if getting vaccinated could lower this risk.”

The study included 1,271,922 people aged 50 or older living in South Korea. Researchers gathered data, from 2012 onwards, on whether people received a live zoster vaccine and combined this with data on their cardiovascular health and data on other factors that can influence health, such as age, sex, wealth and lifestyle.

The study showed that among people who received the vaccine, there was a 23% lower risk of cardiovascular events overall, with a 26% lower risk of major cardiovascular events (a stroke, heart attack or death from heart disease), a 26% lower risk of heart failure and a 22% lower risk of coronary heart disease. The protective effect was strongest in the two to three years after the shingles vaccine was given, but researchers found that the protection lasted for up to eight years. It was particularly pronounced for men, people under the age of 60 and those with unhealthy lifestyles, which may include smoking, drinking alcohol and being inactive.

“Our study suggests that the shingles vaccine may help lower the risk of heart disease, even in people without known risk factors,” Yon said. “This means that vaccination could offer health benefits beyond preventing shingles.

“There are several reasons why the shingles vaccine may help reduce heart disease. A shingles infection can cause blood vessel damage, inflammation and clot formation that can lead to heart disease. By preventing shingles, vaccination may lower these risks. Our study found stronger benefits in younger people, probably due to a better immune response, and in men, possibly due to differences in vaccine effectiveness.

“This is one of the largest and most comprehensive studies following a healthy general population over a period of up to 12 years. For the first time, this has allowed us to examine the association between shingles vaccination and 18 different types of cardiovascular disease. We were able to account for various other health conditions, lifestyle factors and socioeconomic status, making our findings more robust.

“However, as this study is based on an Asian cohort, the results may not apply to all populations. Since the live zoster vaccine is not suitable for everyone, more research on the recombinant vaccine is needed. While we conducted rigorous analysis, this study does not establish a direct causal relationship, so potential bias from other underlying factors should be considered.”

Yon and his colleagues plan to study the impact of the recombinant vaccine to see if it has similar benefits for reducing heart disease.

Illustration by Emily Moskal.