Positive data from novel human challenge models

hVIVO plc

("hVIVO", the "Company" or the "Group")

Positive data from multiple novel human challenge models

hVIVO presentations made at influential ESWI and World Vaccine Congress Europe conferences

hVIVO plc (AIM: HVO), a full-service early phase Contract Research Organisation (CRO) and the world leader in human challenge clinical trials, announces key insights from its scientific presentations at the 10th European Scientific Working Group on Influenza ("ESWI") Conference in Valencia, and the World Vaccine Congress Europe in Amsterdam, which both took place in October 2025.

hVIVO presented positive data from a number of newly developed human challenge models, all demonstrating an acceptable safety and tolerability profile, reinforcing hVIVO's continued world-leading capabilities in accelerating the development of novel challenge agents and its readiness to meet customer demand for innovative and effective clinical trial solutions.

Human Metapneumovirus ("hMPV") challenge model

hVIVO's Senior Study Physician, Dr Alexander Lima, presented the positive findings from the newly developed, and world's only contemporary-strain hMPV human challenge model. The presentation at ESWI, titled, "Disease characteristics and immunological profiles obtained from newly developed hMPV human challenge model", highlighted the model's strong performance using a recent 2a strain, which compared favourably against hVIVO's established RSV A model, a benchmark for model performance for this particular virus family. The model demonstrated high infection and symptomatic disease attack rates and robust AUC virology by qRT-PCR, and is now ready and available for vaccine and antiviral human challenge trials.

SARS-CoV-2 Omicron challenge model

Alex Mann, Senior Director Clinical Science presented, "Development of a SARS-CoV-2 Omicron BA5 human challenge model" at ESWI. This presentation highlighted the success of hVIVO's Omicron human challenge model which performs favourably in seropositive, previously vaccinated participants and confirmed the model's suitability for use in vaccine and treatment studies. A key insight from the presentation was the importance of timing of dosing post-inoculation, particularly in the context of post-exposure prophylaxis. This represents the first commercially available Omicron human challenge model.

Respiratory Syncytial Virus B (RSV B) challenge model

At the World Vaccine Congress Europe, hVIVO's Chief Scientific Officer, Dr Andrew Catchpole showcased the positive results from hVIVO's new RSV B model titled, "High infection rates achieved with the worlds' first RSV B challenge models key component of our RSV-hMPV-PIV combination vaccine efficacy testing platform." The data confirmed the robustness of the RSV B model, which is now available for vaccine and anti-viral efficacy testing. The development of the RSV B and hMPV models, along with the Company's collecting of PIV (parainfluenza virus) clinical samples, has enabled the Company to create a comprehensive efficacy testing platform enabling the Company to test individual components of the next generation combination vaccines under development.

Any interested parties should contact [email protected] to learn more about these new models.

Dr Andrew Catchpole, Chief Scientific Officer of hVIVO, said: "We are delighted to have presented such positive data across three pathogens, hMPV, RSV B, and Omicron, at two of the industry's most influential scientific conferences. These results not only validate our unmatched expertise in designing and delivering new challenge models but also reinforce hVIVO's commitment to accelerating the development of vital vaccines and therapeutics and ensuring we have models that reflect industry's evolving needs."

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Notes to Editors

hVIVO plc (Ticker: HVO) is full-service early phase Contract Research Organisation (CRO) and the global leader in human challenge trials. The company delivers end-to-end clinical development services to a diverse and expanding client base, including seven of the world's ten largest biopharma companies.

hVIVO specialises in conducting human challenge trials across multiple infectious and respiratory indications, leveraging its state-of-the-art quarantine facility in London-the largest of its kind worldwide. The Company also offers comprehensive virology and immunology laboratory services under the hLAB brand.

Through its German subsidiary, CRS, hVIVO operates a 120-bed capacity across Mannheim and Kiel, providing early-phase clinical trial services, including first-in-human and proof-of-concept studies. Its second subsidiary, Venn Life Sciences, offers Early Drug Development Consulting and Biometry services to the biopharma sector.

The Group provides fully integrated drug development solutions from preclinical stages through Phase II trials, alongside patient recruitment via FluCamp. Additionally, its five clinical sites support outpatient Phase II and III trials, ensuring a seamless and efficient pathway from discovery to late-stage development.