Experimental Human Pneumococcal Challenge With SPN3

Inclusion Criteria:• Healthy young adults aged 18-50 years (inclusive). This age range minimises the risk of invasive pneumococcal infection and allows comparison with previously published experimental work done by our group. * Fluent spoken English - to ensure a comprehensive understanding of the research project and their proposed involvement, enabling valid consent to be given. * Access to their own mobile telephone - to ensure safety and timely communication. * Capacity to give informed consent. Exclusion Criteria: * o Currently involved in another study unless observational or non-interventional, excluding the EHPC bronchoscopy study (at the discretion of the study team). This is to ensure no harm comes to the participants through over-sampling. * Participant in any previous EHPC trial in past year * Participant in previous EHPC trial inoculated with SPN3 in the last 3 years * Participant in EHPC Pneumo 2 trial * Vaccination: Previous pneumococcal vaccination PPV23 or PCV13 (routine in babies born in the UK since 2005) or PCV10. This can be self-reported or confirmed from GP questionnaire (GPQ) if deemed necessary at clinician discretion. * Allergy: to penicillin/amoxicillin * Health history (self-reported or confirmed by GPQ or medical summary if felt to be necessary at clinician discretion): * Chronic ill health including immunosuppressive history, diabetes, asthma (on regular medication), recurrent otitis media or other respiratory disease. * Medication that may affect the immune system e.g., steroids, inflammation altering or disease-modifying anti-rheumatoid drugs. * Long term use of antibiotics for chronic infection. * Major pneumococcal illness requiring hospitalisation in the last 10 years. * Other conditions considered by the clinical team as a concern for participant safety or integrity of the study * Significant mental health problems (uncontrolled condition or requiring previous admission to a psychiatric unit) that would impair ability to participate • Direct caring role or close contact with individuals at higher risk of infection during the inoculation period if personal protective equipment (PPE) not worn: * Children under 5 years age * Adults with chronic ill health or immunosuppression * Hospital patients • Smoker: * Current or ex-smoker (daily cigarettes, daily e-cigarettes/vaping and daily smoking of recreational drugs) in the last 6 months. Participants who smoke \<5 cigarettes per week may be included. * Previous significant smoking history (\>20 cigarettes per day for 20 years or equivalent \[\>20 pack years\]). • Biologically female participants of child-bearing potential (WOCBP) who are: * Currently pregnant/lactating * Intending on becoming pregnant during the study * Not deemed to have effective birth control • History of or current drug or alcohol abuse: * Men should not drink \>3 units/day regularly * Women should not drink \>2 units/day regularly * Overseas travel planned in follow up period of study visits * Natural SPN 3 colonisation in baseline nasal wash - if a participant is colonised with non-SPN3 pneumococcus, they can be included as part of exploratory analyses, but would not be included in the primary analysis * STOP criteria - participants who meet STOP criteria at time of screening (Table 3) 6.3 Temporary Exclusion Criteria * Ongoing COVID-19 symptoms (fever, cough, shortness of breath, anosmia or ageusia) or confirmed current COVID-19 infection. Participants with resolved COVID-19 after their UKHSA determined isolation period has ended can be included. * Current/acute illness within 14 days prior to inoculation if COVID-19 negative * Positive COVID-19 swab whether symptomatic or asymptomatic within 10 days of inoculation * Currently isolating following exposure to COVID-19 as per UKHSA guidance * Antibiotic use within 28 days of inoculation. * Participants who have been temporarily excluded at screening may be re-screened at a later date to assess their eligibility at this time for inclusion into the study. At this point, the participant would be re-consented if their initial written consent was given \>4 months prior to this date. * Vaccination 21 days prior to inoculation