Covid boosters tied to small, temporary rise in shingles risk in new study

A large study from the University of Groningen analyzing electronic health records from more than two million people aged 12 and older who had received at least one Covid vaccine found that the risk of shingles within 28 days of vaccination increased by seven percent when all doses were combined, and by 21 percent after the third, or booster, dose of an mRNA vaccine. The researchers emphasized that the increase is small, temporary and limited to certain subgroups, and most cases are treated in general practice rather than requiring hospitalization. The study was published in the peer‑reviewed journal Drug Safety on December 11.

The researchers separated vaccines by type, mRNA versus vector, and by brand. For individuals who received two doses less than 28 days apart, it was difficult to determine which vaccine caused shingles, so the analysis focused on people with a consistent vaccination regimen across type and brand. Among the vaccines by brand, Pfizer/BioNTech accounted for 69.2% of all doses and Moderna 18.6%; the cohort included 54.6% who had two doses. The median age was 51, and the two most common health conditions were cardiovascular disease (25.7%) and chronic lung disease (16.3%). A notably higher risk was observed among men after receiving a vector-based vaccine, with a 38% increase.

The study's key finding was that the risk of shingles within 28 days rose 7% overall, and 21% after a booster dose of an mRNA vaccine. The team separated results by vaccine type and by brand to explore patterns in subgroups. It noted that the increase was small and likely temporary, with most shingles cases managed in primary care rather than requiring hospitalization.

Context outside the Groningen study includes other research on the brain–dementia link. A separate investigation has found that adults aged 50 and older who were hospitalized with shingles were about seven times more likely to develop dementia. A different long‑term study published earlier this year suggested that shingles could trigger early‑onset dementia, particularly among those aged 50 to 65. In the United States, a study using healthcare claims data found no increased dementia risk after Covid vaccination, and vaccination was not linked with a higher risk than flu shots. The FDA is drawing up plans to add a black box warning on Covid vaccines, a move CNN reported could appear on prescribing information if adopted.

The team described a three‑step approach. First, they analyzed all available Covid vaccines, including unknown brands. Second, they divided results by vaccine type—mRNA versus vector. Third, they analyzed results by brand, to identify patterns in subgroups and across regimens. The median age of participants was 51, with most falling within a 32‑year range around the median. The cohort's health profile showed high rates of cardiovascular disease (25.7%) and chronic lung disease (16.3%). Most participants, 1,145,212 people (54.6%), received two vaccine doses. The most commonly given vaccine was Pfizer/BioNTech, which made up 69.2% of all doses, followed by Moderna at 18.6%.

A separate piece of context comes from ongoing debates about dementia prevention. In April, a study spanning more than two decades suggested that shingles could be linked to dementia risk, particularly early-onset forms. In the Italian arm of that work, 132,986 adults aged 50 and older were recruited; of these, 12,088 were hospitalized with shingles. After one year, there was a two‑fold increase in early dementia among those with severe shingles, compared with other groups. Researchers cautioned that more work is needed to determine causality and mechanism.

Regulatory and policy discussions intersect with these findings. The U.S. Food and Drug Administration is examining potential warnings for Covid vaccines, with discussions described by sources familiar with the matter as considering a black box warning—the most prominent safety caution at a drug’s top of prescribing information. Meanwhile, a body of evidence remains mixed: a U.S. claims‑data study found no increased dementia risk after vaccination, and some regional data have suggested spikes in shingles hospitalizations following certain vaccine campaigns.

In the United Kingdom context, an opinion piece published in the Daily Mail argued for broader access to Shingrix on the NHS as a dementia‑prevention tool. The author, former health minister Lord Bethell, described paying privately for the vaccine and urged lowering the age of eligibility to 50–60 to prevent tens of thousands of dementia cases. He cited observational work suggesting the vaccine could cut dementia risk by up to 20% within seven years, and by as much as 50% for vascular dementia. He also shared personal reflections on the potential impact of dementia on public health, while noting the NHS currently restricts access and that policy decisions should reflect emerging evidence.

Alzheimer’s Society researchers caution that while several studies have shown a connection between shingles vaccination and brain health, there is not yet conclusive proof that the vaccine prevents dementia. More research is needed to understand the link, they say, even as they highlight steps people can take today to protect brain health—such as managing blood pressure and cholesterol, exercising regularly, avoiding smoking, limiting excess alcohol, staying socially engaged, and using hearing aids or glasses when needed. Dr. Richard Oakley, Alzheimer’s Society’s Associate Director of Research and Innovation, said: “While several studies have shown a connection, currently we do not have the evidence needed to show for sure that the shingles vaccine prevents dementia. More research is needed to understand the link.”

Health experts emphasize that the potential small, temporary increase in shingles risk must be weighed against the vaccines’ proven benefit in preventing shingles and its complications. The Groningen study’s authors stressed that the observed association does not establish causation, and most shingles cases occur in primary care and do not require hospitalization. Ongoing monitoring and additional research will help clarify any longer‑term implications as vaccination campaigns continue and new data accumulate.