A Study to Evaluate the Safety, Tolerability, and Immunogenicity of V114 in Allogeneic Hematopoietic Stem Cell Transplant Recipients (V114-022/PNEU-STEM)

Inclusion Criteria:

- Received a human leukocyte antigen (HLA) compatible donor including haploidentical and
mismatched (related or unrelated) first allogeneic HSCT (i.e., bone marrow or
peripheral blood stem cell) 90 to 180 days prior to randomization.

- Received the allogeneic HSCT for acute lymphoblastic leukemia (ALL) in first or second
remission, acute myeloid leukemia (AML) in first or second remission, chronic myeloid
leukemia (CML) in first chronic or accelerated phase, Hodgkin's lymphoma,
non-Hodgkin's lymphoma, myelodysplastic syndrome (MDS), myelofibrosis and
myeloproliferative diseases, and non-malignant disease such as aplastic anemia or
sickle cell disease in participants ≥18 years of age and any non-malignant disease for
participants 3 to <18 years of age.

- Life expectancy >12 months after allogeneic HSCT, according to investigator judgement.

- Clinically stable engraftment according to investigator judgment.

- A female participant is eligible to participate if she is not pregnant or
breastfeeding, and at least 1 of the following conditions applies: a) not a woman of
childbearing potential (WOCBP) OR b) a WOCBP who agrees to use acceptable
contraceptive methods during the treatment period and for at least 6 weeks after the
last dose of study intervention.

Exclusion Criteria:

- Receipt of a previous allogeneic HSCT.

- Received allogeneic HSCT with ex-vivo graft manipulation, in vivo T cell depletion
with alemtuzumab, or haploidentical allogeneic HSCT with high dose anti-thymocyte
globulin.

- Received allogeneic HSCT for multiple myeloma or, for participants ≥18 years of age
only, for any nonmalignant diseases except sickle cell disease and aplastic anemia.

- Persistent or relapsed primary disease after allogeneic HSCT.

- History of severe GVHD (Grade 3 or 4 GVHD) after allogeneic HSCT.

- Planned organ transplantation after allogeneic HSCT.

- History of culture-positive pneumococcal disease occurring after allogeneic HSCT.

- Known hypersensitivity to any component of pneumococcal polysaccharide vaccine,
pneumococcal conjugate vaccine, or any diphtheria toxoid-containing vaccine.

- History of acquired immunodeficiency such as documented HIV infection, or anatomic
asplenia.

- Coagulation disorder contraindicating intramuscular vaccinations.

- Severe hepatic impairment (defined as Child-Pugh Class C) at Screening.

- Serum aspartate transaminase (AST) or alanine transaminase (ALT) >5 × upper limit of
normal (ULN) or serum total bilirubin >2.5 × ULN at Screening.

- A WOCBP who has a positive urine or serum pregnancy test before the 1st vaccination.

- Received chimeric antigen receptor T-cell (CAR-T) therapy or checkpoint inhibitor
directed therapy (i.e., anti-Programmed Cell Death (PD)-1) after allogeneic HSCT.

- Received or planned to receive anti-Cluster of Differentiation (CD) 20 B-cell targeted
therapy (e.g., rituximab) after allogeneic HSCT.

- Non-study pneumococcal vaccine administered after allogeneic HSCT, or is expected to
receive non-study pneumococcal vaccine during participation in the study.

- Is currently participating or has participated in an interventional clinical study
with an investigational compound/agent or device within 2 weeks of participating in
this current study, or plans to receive any investigational compound/agent or device
(in addition to existing therapy) within 2 weeks of any vaccination, that in the
opinion of the investigator would interfere with the evaluation of the study
objectives.

- Is, at the time of signing informed consent, a user of recreational or illicit drugs
or has had a recent history (within the last year) of drug or alcohol abuse or
dependence as assessed by the study investigator.

- Has history or current evidence of any condition, therapy, laboratory test result
abnormality, or other circumstance that might expose the participant to risk by
participating in the study, confound the results of the study, or interfere with the
participant's participation for the full duration of the study.

- Is or has an immediate family member who is investigational site or Sponsor staff
directly involved with this study.