TLDR
Older adults who received the newer shingles shot had fewer dementia diagnoses over the following six years than those who received the older shot. This result suggests a possible extra benefit, but researchers must test it in a controlled trial before concluding that the vaccine prevents dementia.
Summary
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1 Study Aim
The authors aimed to determine whether the recombinant shingles vaccine (a vaccine made from selected viral components) was linked to lower dementia risk than the discontinued live vaccine. They used the vaccine switch in the United States as a natural experiment (a real-world change that helps researchers compare similar groups). The study also examined differences by sex and compared shingles vaccines with influenza and tetanus-diphtheria-pertussis vaccines. The study asked whether the newer shingles shot might help people stay free of dementia diagnoses longer.
2 Study Design
The researchers analyzed electronic health records (digital medical records) from the TriNetX US Collaborative Network, covering 62 healthcare organizations. They studied adults aged 65 or older who received their first shingles vaccine. The recombinant-vaccine group included 103,837 people vaccinated from November 2017 through October 2020. The live-vaccine group included 103,837 people vaccinated from October 2014 through September 2017. Propensity-score matching (pairing people with similar recorded characteristics) balanced 60 factors. Researchers tracked first dementia diagnoses from three months through six years after vaccination. They repeated analyses using other matching methods and shorter time periods. The researchers compared two large, similar groups using health records before and after the vaccine change.
3 Findings
The research found that recombinant vaccination was associated with 17% more time without a dementia diagnosis than live vaccination. Among people later diagnosed, this represented 164 additional diagnosis-free days. The association appeared in women and men, but was stronger in women. Both shingles vaccines were linked with lower dementia risk than influenza and tetanus-diphtheria-pertussis vaccines. The result remained similar across multiple checks, including analyses before the COVID-19 pandemic and analyses adjusting for socioeconomic deprivation. Mortality (death from any cause) did not differ between groups. Because this was an observational study (using existing records without assigning treatments), it cannot prove causation. The authors recommend randomized controlled trials and research into possible biological mechanisms. The newer shot was linked to longer dementia-free time, but controlled testing is still needed to prove it prevents dementia.