Study of 10-valent Pneumococcal Conjugate Vaccine (Pneumosil) Administered in a 2+1 Schedule to Healthy Infants

The primary objectives of this study are to evaluate the immunogenicity (antibody response) and safety and tolerability of a 2-dose primary series and booster dose (2+1 schedule) of Pneumosil co-administered with routine pediatric vaccines in healthy infants in The Gambia.

This study will provide data necessary to evaluate the safety and immunogenicity of Pneumosil when administered in an alternative schedule to the 3 dose primary schedule (3+0) evaluated in the Phase 3 pivotal trial (VAC-056; NCT03197376) - namely in a 2 dose primary and booster (2+1) schedule - and compare immunogenicity to that of both currently licensed second-generation pneumococcal conjugate vaccines (Synflorix and Prevenar 13) administered in the same 2+1 schedule.

In this prospective, single center, randomized, active-controlled, observer-blind, Phase 3 descriptive study, 660 healthy Gambian pneumococcal conjugate vaccine (PCV)-naïve infants will be randomized 1:1:1 to receive 3 doses of either Pneumosil, Synflorix or Prevenar 13 at 6 weeks, 14 weeks and 9-10 months of age. Standard Expanded Program on Immunization (EPI) vaccinations in The Gambia will be given concomitantly with all 3 doses of study vaccine.

The booster vaccination window was extended up to 18 months of age due to a pause in the study due to the coronavirus disease 2019 (COVID-19) pandemic. The study schedule for participants is as follows:

* Age 6 weeks: First primary vaccination dose administered
* Age 14 weeks: Second primary vaccination dose administered (8 weeks after first primary dose)
* Age 18 weeks: Blood sample for immunogenicity testing (4 weeks after second primary dose)
* Age 9-18 months: Blood sample for immunogenicity testing and booster vaccination dose administered
* Age 10-19 months: Blood sample for immunogenicity testing (4 weeks after booster dose)

Eligibility Criteria:
Inclusion Criteria:

* Healthy infants based on medical history and clinical assessment.
* Between 6 and 8 weeks (ie 42 to 56 days) old, inclusive.
* Subject's parent must provide voluntary written/thumb-printed informed consent and be willing to comply with study requirements and procedures.
* Subjects must have been born full-term, have a weight-to-height Z score of ≥ -2 at the time of enrollment (WHO child growth standard), and be ≥ 3.5 kg at randomization.
* Subject's parents must be available for the duration of trial participation

Exclusion Criteria:

* Use of any investigational medicinal product prior to randomization.
* Previous vaccination against or infection with S. pneumoniae.
* History of anaphylactic shock or an allergic reaction to any prior vaccination.
* Any fever, illness (including malaria).
* Receipt of another study vaccine within 30 days of study start.
* Chronic administration of an immunosuppressant or administration of immunoglobulins
* History of blood disorder, primary immunodeficiency, or a sibling who has such a diagnosis or who died suddenly without apparent cause.
* History of meningitis, seizures or any neurological disorder.
* Exposure to human immunodeficiency virus (HIV) by history.