PREVENTING PNEUMOcoccal Disease Through Vaccination (Study 2)

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.