Shingles cases among younger Australians have gradually increased over the past two decades, prompting experts to ask what is happening.

In 2006, Australia reported 299 shingles cases among adults aged 25-49 years. The number of cases in this group was 1877 in 2015 and 5249 in 2020. So far this year, 2493 cases have been reported to Australia’s National Notifiable Disease Surveillance System.

However, the true burden of the disease is unknown because herpes zoster is not a notifiable disease in all states and territories. It is not notifiable in New South Wales (NSW), for example. Moreover, not everyone who gets shingles visits the doctor.

While there’s no surveillance in NSW, the country’s most populous state, data from NSW Health show an increase in emergency visits assigned a diagnosis of shingles among several age groups between 2018 and 2023. For example, in 2018, 192 people aged 40-44 years visited the emergency department for shingles compared with 250 in 2023.

An Illusory Increase?

The increase in shingles, which is caused by the reactivation of dormant varicella-zoster virus in nerve tissue, has left experts speculating whether the rise in cases represents a true increase or rather increased diagnosis and reporting.

Stress, a rise in the number of patients taking immunosuppressants, and an increase in diabetes could be contributing to the increase in shingles, Allen Cheng, MBBS, PhD, director of Monash Infectious Diseases at Monash Health in Melbourne, told Medscape News Australia.

“A rise in stress is possible, and there are now more people who are immunosuppressed with diseases that, in time gone by, we could not treat, such as rheumatoid arthritis. Diabetes is also becoming more common in young people, and that certainly can cause shingles,” he said.

“But it’s really hard to tell what is happening. Shingles is one of those diseases where not all go and see a doctor. The doctor may or may not report it. We’re not really sure.”

The introduction of the chickenpox vaccine in Australia in 2005 could also be a factor, he added. While children who received the chickenpox vaccine won’t get shingles later in life, some patients had chickenpox before the childhood vaccination program and therefore carry the dormant virus, which can later reactivate and cause shingles.

“There was a lot of concern early on with the chickenpox vaccine that it would cause more shingles. That’s because when adults are exposed to chickenpox, it acts like a booster of immunity and helps control shingles. It’s a theory and hard to know to what extent it could be contributing,” Cheng said.

Calculating Disease Burden

The true burden of the disease is likely higher than reported, according to Bette Liu, MBBS, associate professor of infectious diseases and immunization at the UNSW Sydney in Kensington and senior medical officer at the National Centre for Immunisation Research and Surveillance.

“I understand that the data on the potentially rising rates of shingles in young adults come from notifications data that tend to underreport shingles cases (because they are not collected in all jurisdictions in Australia) and rely on healthcare provider report, as most diagnoses of shingles do not involve laboratory confirmation,” she said.

“The issue is that reporting can also change over time with greater awareness of disease. The true burden is likely higher for all groups of individuals.”

Sarah Annesley, PhD, Tracey Banivanua Mar Research Fellow in cell and molecular biology at La Trobe University in Melbourne, is anecdotally hearing about more and more younger people with shingles, including a colleague of hers in her forties.

Outbreaks in younger patients are typically milder and resolve faster than in older adults. Still, this time of life can be stressful: People of this age group are often focused on raising a family or building a career. If the vaccine is shown to be safe and effective in younger age groups, it could be extended to include patients aged 30 years or older, said Annesley.

Vaccine Uptake Suboptimal

In 2023, the varicella virus recombinant vaccine, sold as Shingrix, replaced the live attenuated herpes zoster vaccine Zostavax on the National Immunisation Program (NIP).

Zostavax had been provided free of charge for immunocompetent people aged 70 years or older. Today, a two-dose course of Shingrix, which provides around 10 years of protection, is available for free for patients aged 65 years or older, Aboriginal and Torres Strait Islander patients aged 50 years, and patients aged 18 years or older who are considered to have increased risk for herpes zoster due to an underlying condition or immunomodulatory or immunosuppressive treatments.

The addition of Shingrix to the NIP has led to a significant spike in uptake, research has found, with one third of eligible adults receiving at least one dose in the program’s first year. This uptake has translated into fewer cases among older people, as recent data show.

But that’s far from optimal coverage, and it must be taken into consideration when looking at expanding free vaccine eligibility, Meru Sheel, PhD, leader of the Infectious Diseases, Immunisation, and Emergencies Group at The University of Sydney in Sydney, told Medscape News Australia.

“We don’t have good coverage for the funded vaccine right now,” she said. “So clearly, a free vaccine is not the only thing that drives people.”

Shingrix was only approved for use in adults aged 50 years or older in Australia. There could be an argument for making it free for patients aged 50 years or older, but important factors must be considered, said Sheel.

“The challenge is the duration of protection (the sweet spot) and the cost. It’s a very expensive vaccine. So if you get the vaccine at age 50 years and your risk of getting shingles goes up at 60 or 70 years, you would then need a booster. That’s two doses of the vaccine you have to get,” she said. Two doses of the vaccine cost around $560.

Expanding Eligibility

For now, Sheel would like Australia to have good surveillance data. “The crux of the issue is that we have incomplete reporting. It would be good to have good surveillance data across all states and territories. We probably do need it,” she said.

“We’re obviously seeing the notifiable cases go up, but we don’t have any kind of good data to say if it’s a real increase or not because we don’t have denominator data of how many people are getting tested; it’s not reported consistently, and it’s reported as chickenpox or shingles or unclassified.”

Cheng has mixed feelings about expanding free vaccine eligibility to patients aged 50 years or older. He comes back to finding the sweet spot, like Sheel, and weighing the high cost against a smaller benefit. “The thing we must remember is that the risk of shingles increases with age. The issue is if you give the vaccine early, you’re not protected at the time and you’re most likely to get it, so it’s not going to work at the time you really want it to work,” he said.

“Whether the vaccine is made available for free in Australia depends on meeting cost-effectiveness criteria, [and] part of that consideration would be the incidence and severity of disease in all adults aged 50-65 years who currently aren’t included in the funded groups under our NIP,” Liu added.

The recombinant shingles vaccine protects against a painful blistering virus that can — in some patients — cause long-term complications, including postherpetic neuralgia. Moreover, research has shown that it holds promise in reducing dementia risk.

For Cheng, the research holds promise for a disease that is the leading cause of death in Australia. “There’s still a lot that we don’t know, but the research strongly suggests that it’s protective against dementia,” he said. “With more research, if it becomes a true effect, then it has a lot of repercussions for the future.”

Cheng was a member of the Australian Technical Advisory Group on Immunisation that provided advice on Shingrix to the Pharmaceutical Benefits Advisory Committee in 2023. He holds contracts for disease surveillance with the Commonwealth and is a member of the Communicable Diseases Network Australia. Liu received funding, paid her institution, from the Australian National Health and Medical Research Council and the Medical Research Future Fund for research on vaccine program evaluation. Annesley and Sheel reported no relevant financial relationships.