Inclusion Criteria:  Healthy adults aged 18-50 years (inclusive) Fluent spoken English - to ensure a comprehensive understanding of the research project and their proposed involvement Capacity to provide written informed consent Females of childbearing potential with a negative urine pregnancy test at screening and willing to practice adequate birth control measures during the study.  Exclusion Criteria:  Be currently involved in another study unless observational or non-interventional. Exceptions are the EHPC bronchoscopy study and COVID-19 observational and interventional trials. The exceptions will be applied at the discretion of the Chief Investigator to ensure no harm comes to the participants (e.g. excessive blood sampling)  Be a participant in a previous EHPC trial within the last 3 years (at the discretion of the study team).  Vaccination (self-reported or confirmed from GP questionnaire [GPQ] or medical summary if deemed necessary at clinician discretion): Have had any previous pneumococcal vaccination (including in a research study). Allergy: Have allergy to penicillin or amoxicillin.  Have previous anaphylaxis or severe adverse reaction to any component/excipient of the vaccines or to any vaccine.  • Health history (self-reported by the participant or confirmed in GPQ or medical summary if deemed necessary at clinician discretion): Ill health including but not limited to:  Asplenia or dysfunction of the spleen. Chronic respiratory disease (e.g. asthma [on medication], COPD, emphysema, bronchiectasis). Chronic heart disease (e.g. angina, ischaemic heart disease, chronic heart failure) [controlled stable hypertension may be included]. Chronic kidney disease (e.g. nephrotic syndrome, kidney transplant, on dialysis). Chronic liver disease (e.g. cirrhosis, biliary atresia, hepatitis). Chronic neurological conditions Connective tissue disease Dementia Diabetes mellitus (including diet controlled). Immunosuppression or history of receiving immunosuppressive therapy. Individuals with cochlear implants. Individuals with major cerebrospinal fluid leaks (e.g. following trauma, major skull surgery, or requiring CSF shunt).  Recurrent otitis media.  Have any uncontrolled medical/surgical conditions (such as but not restricted to mental health conditions, epilepsy, narcolepsy or chronic pain) at the discretion of the study doctor. Major pneumococcal illness requiring hospitalisation within the last 10 years Other conditions considered by the clinical team as a concern for participant safety or integrity of the study. Taking medication: That may affect the immune system e.g. steroids, inflammation altering (e.g. nasal steroids, Roaccutane) or disease-modifying anti-rheumatoid drugs. Long-term use of antibiotics (see also section 6.3 Temporary exclusion criteria). Nitroglycerin  That affects blood clotting (any oral/injectable anticoagulants [except aspirin]).  Female participants who are pregnant, lactating or intending on becoming pregnant during the study. Direct caring role or close contact with individuals at higher risk of infection (during the challenge period) Children under 5 years age. Chronic ill health or immunosuppressed adults.  People that are part of the extremely vulnerable group as defined by Public Health England (PHE)  • Smoker:  Current or ex-smoker (regular cigarettes/cigars/e-cigarette/vaping/smoking of recreational drugs) in the last 6 months.  Previous significant smoking history (more than 20 cigarettes per day for 20 years or the equivalent [>20 pack years]).  History or current drug or alcohol abuse (frequently drinking alcohol): men and women should not regularly drink >3 units/day and >2 units/day respectively) at discretion of the clinician. Significant mental health problems (uncontrolled condition or previous admission in a psychiatric unit, at the discretion of the clinician) that would impair the participant's ability to participate in the study Overseas travel planned: Overseas travel during the follow-up period Part A or Part B. Participants who meet STOP criteria at the time of screening, as detailed in Table 4. Any other issue which, in the opinion of the study staff, may Put the participant or their contacts at risk because of participation in the study, Adversely affect the interpretation of the study results, or Impair the participant's ability to participate in the study.