Background on Multiple Sclerosis and the Global Burden
Multiple sclerosis (MS) is a chronic autoimmune disorder in which the immune system mistakenly attacks the protective myelin sheath surrounding nerve fibers in the brain and spinal cord. In the United Kingdom, MS affects roughly 1 in 500 people, and the disease is responsible for significant disability, loss of productivity, and health‑care costs. Over the past decades, advances in immunomodulatory drugs have improved outcomes, yet many patients still experience disease‑relapsing activity and long‑term neurological decline.
Why Target the Epstein‑Barr Virus?
Recent epidemiological studies have highlighted a strong association between infection with Epstein‑Barr virus (EBV) and the development of MS. More than 90 per cent of adults in the UK have been infected with EBV, yet the virus remains dormant in B lymphocytes for the rest of life. The hypothesis is that re‑activation of the virus or an aberrant immune response to it triggers the autoimmune cascade that damages myelin.
Because nearly everyone has been exposed to EBV, treating the underlying infection—or preventing its re‑activation—offers a novel strategy to change the disease trajectory of MS. A vaccine that helps the immune system keep the virus suppressed could thus reduce or even halt the emergence of new lesions that lead to disability.
The Horizon Trial – A First‑In‑Human Phase 2 Study
The University of Edinburgh, in partnership with Moderna and supported by the UK Health Security Agency, is leading the Horizon trial. The investigational candidate is a messenger‑RNA (mRNA) vaccine designed to boost the body’s humoral and cellular response against EBV.
Trial Design and Objectives
- Phase and Scope: Early‑stage Phase 2, randomized, double‑blind, placebo‑controlled.
- Primary Endpoint: Safety and tolerability of the investigational vaccine in people newly diagnosed with MS.
- Secondary Endpoint: Reduction in new MRI activity and clinical relapse rates over two and a half years.
- Global Reach: Up to 180 participants across ten UK sites, including the University of Edinburgh, with potential expansion to international sites if early data are promising.
Eligibility and Participant Flow
Prospective volunteers must be:
- Between 18 and 55 years old.
- Diagnosed with relapsing‑remitting MS within the past two years.
- EBV seropositive (which is nearly universal in the UK).
- Free from serious medical comorbidities that could interfere with immunization safety.
Those enrolled will receive either the investigational mRNA vaccine or a saline placebo in a 1:1 allocation. The study will involve 14 scheduled clinic visits and 21 telephone contacts over two and a half years, enabling close monitoring for safety signals and efficacy outcomes.
What Participants Will Experience
Clinical monitoring will include:
- Physical examinations and neurological assessments at each visit.
- MRI scans to detect new brain or spinal cord lesions.
- Blood draws to measure humoral and cellular immune responses to EBV.
- Standardised questionnaires to capture quality‑of‑life, fatigue, and disability scores.
Safety data such as injection‑site reactions, fever, or more serious adverse events will be recorded in real time, providing rapid insights into tolerability. The investigators hope to see a measurable reduction in MRI‑defined activity and clinical relapses in the vaccine arm compared with placebo.
Collaborative Forces Driving the Trial
The Horizon trial exemplifies how academia, industry, and government can converge to accelerate vaccine development for non‑communicable diseases:
- University of Edinburgh: Clinical trial steering, recruitment, and data collection.
- Moderna: Sponsorship, vaccine manufacturing, and scientific guidance.
- UK Health Security Agency, NHS Research Scotland, and the National Institute for Health and Care Research: Oversight and strategic alignment with national research priorities.
Chief Scientist Professor Dame Anna Dominiczak has highlighted that being the first non‑US country to open a trial of this type gives the UK a strategic edge in vaccine science and positions it as a hub for future pandemics and chronic disease innovations.
Implications for MS Management and Prevention
If the vaccine demonstrates safety and a tangible effect on relapse rates, it could shift the therapeutic paradigm from general immunosuppression to targeted immunomodulation against a specific viral trigger.
Such a breakthrough would:
- Reduce reliance on broad‑acting disease‑modifying therapies with their associated side‑effect profiles.
- Offer a pre‑emptive strategy for patients diagnosed early, potentially slowing long‑term progression.
- Open doors for population‑wide vaccination against EBV as a public‑health measure to curb MS incidence, a possibility that has begun to attract attention from research funding bodies and policy makers.
How to Get Involved and Stay Informed
Research participants, patient advocacy groups, and clinicians all have avenues to engage:
- Ask your neurologist about whether you meet eligibility criteria for Horizon. Many routine MS clinics now screen for MS‑related research participation.
- Visit NIHR Be Part of Research to learn more about application requirements and navigate the enrollment process.
- Follow the University of Edinburgh’s news portal for real‑time updates on trial milestones, safety reports, and emerging scientific publications.
- Join online communities such as the UK MS Society forums or moderated patient networks to share experiences and insights with peers and researchers.
Explore participation options for the Horizon trial to see if you qualify and to contribute to a landmark study that could transform MS care.
Next Steps and Monitoring Outcomes
The Phase 2 cohort will complete the study in late 2027, with a final safety and efficacy data set expected soon thereafter. Successful outcomes will pave the way for a Phase 3 expansion, potentially expanding to a global hit‑list of sites, while gathering more robust evidence for regulatory approval and eventual clinical accessibility.
Researchers will also examine ancillary benefits such as changes in immune profile markers that could explain the pathophysiology of MS beyond EBV suppression, providing a richer understanding of disease mechanism.
For clinicians, these findings could soon inform guideline updates on early intervention strategies. For patients, the prospect of a targeted vaccine offers a tangible hope of reducing future disability.
Connecting with the Community and Sharing Your Story
- Have questions about the Horizon trial? Reach out to the University’s research office for personalized guidance.
- Share your own MS journey or experience with vaccine trials by commenting below or joining moderated discussion forums; your voice can help shape future research priorities.
- Subscribe to our email alerts on MS research by signing up at the University of Edinburgh’s research newsletter portal to stay updated on upcoming trials, new therapies, and key findings.
By staying engaged, you help accelerate the development of disease‑specific vaccine strategies that may ultimately provide broader public‑health benefits.
Thank you for reading—your participation and curiosity are vital to advancing the science of multiple sclerosis.
