Vaccines are traditionally developed to prevent specific infectious diseases, but occasionally, emerging evidence reveals additional health benefits, what scientists and regulators may refer to as “dual-use” effects. A timely example is the shingles vaccine, originally approved to prevent herpes zoster and its complications, which is now being studied for a potential secondary benefit: reducing the risk of dementia. This has sparked interest in how such a vaccine might formally gain recognition for a dual-use indication.
To understand the process, we must first recognize what qualifies as “dual use” in the context of public health. Dual-use status means a single intervention, such as a vaccine or drug, demonstrates clinically significant benefits for more than one medical condition. In the case of the shingles vaccine, large observational studies suggest a 20% lower incidence of dementia in vaccinated individuals compared to those who did not receive the vaccine (Griffiths et al., 2022). However, identifying a promising association is just the beginning.
Step 1: Generating Observational and Mechanistic Evidence
The path to dual-use recognition typically begins with population-level data. Researchers analyze healthcare records, registries, or cohort studies to detect patterns in health outcomes. The Welsh study published in BMJ used linked health records of over 280,000 people aged 65 and older to show a statistically significant reduction in dementia diagnoses among those who received the shingles vaccine (Griffiths et al., 2022).
Parallel to epidemiological evidence, mechanistic studies must explore the biological plausibility of the secondary effect. For shingles and dementia, proposed mechanisms include reduced central nervous system inflammation due to suppressed reactivation of the varicella-zoster virus and possible enhancement of immune function through vaccine-induced “trained immunity” (Itzhaki, 2020; Readhead et al., 2018).
Step 2: Controlled Clinical Trials and Data Replication
While observational studies are informative, regulatory agencies require stronger evidence, usually in the form of randomized controlled trials (RCTs), before recognizing an additional indication. This step involves designing trials where dementia incidence is a pre-specified outcome, ideally across diverse populations.
Replication of results in different countries and healthcare systems strengthens the case. It also allows researchers to rule out confounding factors such as socioeconomic status, healthcare access, and underlying health conditions.
Step 3: Regulatory Review and Label Expansion
Once sufficient evidence is gathered, manufacturers or independent researchers may submit data to regulatory authorities like the FDA, EMA, or MHRA to request label expansion. This process involves a formal application, including data on safety, efficacy, and a scientific rationale for the new indication. Regulatory bodies review the data, assess benefit-risk profiles, and may convene advisory panels before granting approval.
Currently, the shingles vaccine is not licensed for dementia prevention, but growing interest from the scientific community could push stakeholders to initiate this process if further studies confirm causality.
Step 4: Policy Adoption and Clinical Guidelines
If approved for a secondary use, the vaccine’s new role would be integrated into public health guidelines and clinical practice. Agencies like the CDC’s Advisory Committee on Immunization Practices (ACIP) may then update recommendations to reflect its dual benefit.
Conclusion
The potential dual-use recognition of the shingles vaccine underscores the evolving nature of medical innovation, where a single intervention can deliver multiple public health benefits. While the journey from observational insight to regulatory approval is rigorous, it reflects the scientific and ethical responsibility to ensure that expanded indications are both evidence-based and clinically meaningful. As the research community continues to explore the link between shingles vaccination and reduced dementia risk, the path to formal recognition will depend on robust data, regulatory engagement, and stakeholder collaboration.
At EMMA International, we specialize in guiding life science companies through the complexities of regulatory strategy, clinical trial design, and label expansion. Contact us at (248) 987-4497 or info@emmainternational.com to learn how we can support your pursuit of innovation, compliance, and broader therapeutic impact.
References:
Griffiths, J. C., et al. (2022). Association between shingles vaccination and reduced dementia risk in Wales: A retrospective cohort study. BMJ, 378:e071604. https://doi.org/10.1136/bmj-2021-071604
Itzhaki, R. F. (2020). Herpes simplex virus type 1 and Alzheimer’s disease: Possible mechanisms and signposts. F1000Research, 9, F1000 Faculty Rev-149. https://doi.org/10.12688/f1000research.21880.1
Readhead, B., et al. (2018). Multiscale analysis of independent Alzheimer’s cohorts finds disruption of molecular, genetic, and clinical networks by human herpesvirus. Neuron, 99(1), 64–82.e7. https://doi.org/10.1016/j.neuron.2018.05.023
