Shingles vaccine may increase mild shingles risk for a few weeks, new data shows

Sydney Morning Herald

14-06-2025

The company said many of the cases might be rashes that were misdiagnosed by GPs as shingles; rashes are a noted side effect of the vaccine.
But the researchers – which includes the head of signal reporting at Victoria's Vaccine Safety Service – are confident about their data.
Australia's drug regulator, the Therapeutic Drugs Administration, confirmed it too had 'found evidence of a possible temporal association' between the vaccine and shingles and was investigating.
The new data shows a 16-times increased risk of developing shingles in the three weeks following the first dose of Shingrix, compared to the period before vaccination.
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The risk only effects people aged over 65. After three weeks, the vaccine's protection kicks in and the risk of developing shingles drops dramatically.
The researchers do not yet have absolute risk figures. But other studies suggest that for every 1000 unvaccinated people aged between 60 and 69, there will be about 150 new cases a year. Shingrix cuts cases of shingles by 97.4 per cent in that age group, according to a large clinical trial.
'It does not change the overall benefit this vaccine has been proven to have. It's more about letting people know it is possible,' said Professor Jim Buttery, head of epidemiology and signal detection at the Victorian government's Immunisation Safety Service. 'There is a very short-term increased risk, followed by a much longer period of increased protection.'
The data is not yet conclusive and has not shown up in vaccine surveillance programs in other countries rolling out Shingrix.
'I find that data very strange, and biologically difficult to understand,' said Professor Tony Cunningham, director of the Centre for Virus Research at The Westmead Institute for Medical Research. 'It does not quite fit with the trials or the effectiveness studies.'
Cunningham led the global clinical trials that showed Shingrix was safe and effective; they did not find any evidence of shingles reactivation following vaccination.
The Victorian researchers used two datasets for their study, a database of GP visits from Outcome Health and a second dataset drawn from hospital presentations and lab-confirmed cases of shingles.
The increased risk showed up strongly in the GP dataset, but only slightly in the hospital dataset.
The researchers believe this means nearly all the vaccine-related cases are mild, as the patients are going to GPs rather than to hospital. They did not see any increased risk for postherpetic neuralgia, a nasty chronic pain that often is a complication of severe shingles.
'We still believe the true effect possibly lies between the two datasets, but we believe the primary care dataset is the most important to explore this,' said Shetty.
The mildness of the cases may also explain why other countries have not recorded similar increases in shingles.
Because people are not turning up to hospital, they might have been missed by data-collectors. Most countries don't monitor GP visits – Australia's database is brand new.
That's a strength of the study, but it could also be a flaw.
Cunningham said many doctors misdiagnosed a rash or other symptoms as shingles.
Following the vaccine's 2018 rollout in Germany, some patients reported shingles-like rashes following the jab. But a later investigation revealed half those cases were misdiagnosed.
However, Buttery pointed to a 2007 study showing GPs had a 90 per cent accuracy rate diagnosing shingles. The signal in his data is so strong it would still stand even if many cases were misdiagnosed, he said.
It remains unclear what might be causing the increased risk of shingles following the vaccine.
'The answer is, we essentially don't know. The immunologists we've worked with have theories, but no one knows,' said Buttery.
GSK, the manufacturer of Shingrix, said there was 'currently no established biological mechanism through which Shingrix, a non-live vaccine, would cause shingles'.
The team's hypothesis focuses on age and the design of the vaccine.
Shingles is caused by a reactivation of the Varicella-Zoster virus.
We first encounter VZV as children, when the virus causes chickenpox. The nasty red rash fades, but the virus hangs around – slinking off into our nerve cells, where it is out of the reaches of our immune system.
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As we age, our immune systems naturally lose their punch – a phenomenon known as immunosenescence. Eventually, our immune system might weaken so much VZV is able to reactivate, causing shingles.
Why would the vaccine cause reactivation? One possibility: the vaccine's adjuvant may weaken cellular immunity for a small time period. In people who already have weakened immunity, that short period could allow the virus, in rare cases, to reactivate.
In a time when vaccine misinformation is rampant, the researchers said the close tracking and disclosure of possible side effects was evidence of the safeguards built into Australia's vaccine system.
'Work like ours is very important to maintain vaccine confidence and vaccine trust, and help patients make informed decisions,' said Shetty.