Study to Evaluate a 25-Valent Pneumococcal Conjugate Vaccine

Inclusion Criteria: * Healthy adults who are 18 through 40 years old on the day of randomization (Day 1). * Subject, or subject's LAR, must provide voluntary written informed consent for the subject to participate in the study. * Subject or subject's LAR must be able to comprehend and comply with study requirements and procedures and must be willing and able to return for all scheduled follow-up visits. * There will be an allowance though not a requirement for COVID-19 vaccination in all participants in compliance with Canadian national recommendations. * Adult female subjects who are not surgically sterile must have a negative serum pregnancy test at screening and negative urine pregnancy test prior to vaccination. Exclusion Criteria: * Use of any investigational medicinal product within 90 days prior to randomization or planned use of such a product during the period of study participation. * Adults who have previously been vaccinated against S. pneumoniae. * History of microbiologically confirmed invasive disease caused by S. pneumoniae. * History of allergic disease or history of a serious reaction to any prior vaccination or known hypersensitivity to any component of the study vaccines. * Known or suspected allergy to PEG. * History of angioedema. * Any abnormal vital sign deemed clinically relevant by the PI. * Acute illness (moderate or severe) and/or fever (body temperature of ≥ 38.0°C) * Use of antibiotics (oral or parenteral) within 5 days of randomization. * History of administration of any non-study vaccine (e.g. influenza; COVID-19 vaccine) within 14 days of first administration of study vaccine or planned vaccination prior to 14 days post-vaccination blood draw. * Chronic administration (defined as more than 14 consecutive days) of immunosuppressant or other immune modifying drugs prior to the administration of the study vaccine (and within the 6 months prior to administration of the study vaccine in the case of adults), including the use of glucocorticoids. The use of topical and inhaled glucocorticoids will be permitted. * Administration of immunoglobulins and/or any blood products within the 6 months prior to administration of the study vaccine, or anticipation of such administration during the study period. * History of known disturbance of coagulation or blood disorder that could cause anemia or excess bleeding (e.g., thalassemia, coagulation factor deficiencies, severe anemia). * Any medical or social condition that in the opinion of the PI , may interfere with the study objectives, pose a risk to the subject, or prevent the subject from completing the study follow-up. * Subject is an employee of, or direct descendant (child or grandchild) of any person employed by the Sponsor, PATH, the CRO, the PI. * Any screening laboratory test result outside the normal range and with toxicity score ≥ 2, unless allowed by the PI and PATH Medical Officer when a toxicity score and the normal range overlap significantly. A subject may repeat each laboratory assessment once during the screening period, with the most recent laboratory value being used for evaluation of exclusion criteria. * A positive serologic test for human immunodeficiency virus (HIV)-1 or HIV-2 (HIV 1/2 Ab), hepatitis B (HBsAg) or hepatitis C (HCV Ab). * History of malignancy, excluding non-melanoma skin and cervical carcinoma in situ. * Recent history (within the past year) or signs of alcohol or substance abuse. * History of major psychiatric disorder. * Female adult subjects who are pregnant or breastfeeding