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Updated: Jul 6, 2025
Experimental Human Pneumococcal Carriage
Published on: February 15, 2013
Serotype 3 Experimental Human Pneumococcal Challenge (EHPC) study protocol: dose ranging and reproducibility in a
Phoebe Hazenberg1, Ryan E Robinson1,2, Madlen Farrar1
1Liverpool Vaccine Group, Liverpool School of Tropical Medicine, Liverpool, UK.
Introduction:
Since the introduction of pneumococcal conjugate vaccines, pneumococcal disease rates have declined for many vaccine-type serotypes. However, serotype 3 (SPN3) continues to cause significant disease and is identified in colonisation epidemiological studies as one of the top circulating serotypes in adults in the UK. Consequently, new vaccines that provide greater protection against SPN3 colonisation/carriage are urgently needed. The Experimental Human Pneumococcal Challenge (EHPC) model is a unique method of determining pneumococcal colonisation rates, understanding acquired immunity, and testing vaccines in a cost-effective manner. To enhance the development of effective pneumococcal vaccines against SPN3, we aim to develop a new relevant and safe SPN3 EHPC model with high attack rates which could be used to test vaccines using small sample size.
Methods And Analysis:
This is a human challenge study to establish a new SPN3 EHPC model, consisting of two parts. In the dose-ranging/safety study, cohorts of 10 healthy participants will be challenged with escalating doses of SPN3. If first challenge does not lead into colonisation, participants will receive a second challenge 2 weeks after. Experimental nasopharyngeal (NP) colonisation will be determined using nasal wash sampling. Using the dose that results in ≥50% of participants being colonised, with a high safety profile, we will complete the cohort with another 33 participants to check for reproducibility of the colonisation rate. The primary outcome of this study is to determine the optimal SPN3 dose and inoculation regime to establish the highest rates of NP colonisation in healthy adults. Secondary outcomes include determining density and duration of experimental SPN3 NP colonisation and characterising mucosal and systemic immune responses to SPN3 challenge.
Ethics And Dissemination:
This study is approved by the NHS Research and Ethics Committee (reference 22/NW/0051). Findings will be published in peer-reviewed journals and reports will be made available to participants.
Insights
Developing a new pneumococcal serotype 3 (SPN3) Experimental Human Pneumococcal Challenge model is crucial for testing novel vaccines. This study aims to establish a safe and effective SPN3 challenge model with high colonization rates in adults.
Area of Science:
- Infectious Diseases
- Vaccinology
- Microbiology
Background:
- Pneumococcal conjugate vaccines have reduced disease rates for many serotypes, but Streptococcus pneumoniae serotype 3 (SPN3) remains a significant public health concern, particularly in the UK.
- SPN3 is a leading cause of invasive pneumococcal disease and is frequently detected in adult colonization studies, highlighting an unmet need for effective SPN3 vaccines.
- The Experimental Human Pneumococcal Challenge (EHPC) model offers a controlled environment to assess pneumococcal colonization and vaccine efficacy.
Purpose of the Study:
- To develop and validate a novel, safe, and reproducible SPN3 Experimental Human Pneumococcal Challenge (EHPC) model.
- To identify an optimal SPN3 dose and inoculation strategy that achieves high nasopharyngeal colonization rates in healthy adults.
- To facilitate the testing of new SPN3 vaccines with a reduced sample size.
Main Methods:
- A dose-ranging and safety study involving healthy participants challenged with escalating doses of SPN3.
- Nasopharyngeal colonization assessed via nasal wash sampling, with participants potentially receiving a second challenge if initial colonization fails.
- A subsequent cohort of 33 participants to confirm colonization rate reproducibility using the determined optimal dose and regimen.
Main Results:
- The study's primary outcome is the determination of the optimal SPN3 dose and inoculation method for achieving high experimental nasopharyngeal colonization rates.
- Secondary outcomes include evaluating the density and duration of SPN3 colonization and characterizing the associated mucosal and systemic immune responses.
- The established EHPC model is intended to enable efficient vaccine testing against SPN3.
Conclusions:
- A robust SPN3 EHPC model is essential for advancing the development of next-generation pneumococcal vaccines.
- This validated model will accelerate the evaluation of vaccine candidates targeting SPN3 colonization and carriage.
- The findings will contribute to reducing the burden of SPN3-related diseases through improved vaccine strategies.
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