The main purpose of this study is to evaluate the immune response and safety of a booster dose of the meningococcal group B vaccine, rMenB+OMV NZ (also known as Bexsero), in adolescents and young adults aged 10 to 20 years. This study focuses on individuals who were first vaccinated with rMenB+OMV NZ as infants. The primary hypothesis is that a booster dose of the vaccine will elicit a stronger immune response in these primed individuals compared to those who have never received any group B meningococcal vaccine, referred to as 'nave' participants.

Inclusion Criteria:

Participants are eligible to be included in the study only if all of the following criteria apply:

For primed group only:

• Participated who were primed with rMenB + OMV NZ in only either 3+1 or 2+1 schedule during the first 2 years of life as confirmed by electronic or paper vaccination record.

OR

For naïve group only:

• Electronic or paper vaccination record confirmed participant who has never received any group B meningococcal vaccine and is recruited in the same country as primed participants.

For all participants:

• Participants and/or participants' parent(s)/ legally acceptable representative(s) (LAR[s]), who, in the opinion of the investigator, can and will comply with the requirements of the protocol
• Written or witnessed/thumb printed informed consent obtained from the participant / parent(s)/LAR(s) of the participant prior to performance of any study-specific procedure.
• Written informed assent obtained from the participant (if applicable) along with informed consent from the participant's parent(s)/LAR(s) prior to performing any study specific procedure.

Note: For age 10-16 years, parents or LAR to give consent along with participants, based on country regulations for participants and for >16/18 to 20 years, participants give consent independent of parents/LARs, or as per local country regulations.

• A male or female between, and including, 10 and 20 years of age at the time of the first study intervention administration.

• Female participants of non-childbearing potential may be enrolled in the study. Non-childbearing potential is defined as pre-menarche, hysterectomy, bilateral ovariectomy.

• Female participants of childbearing potential may be enrolled in the study, if the participant:

  • has practiced adequate contraception for 1 month prior to study intervention administration, and
  • has a negative pregnancy test on the day of study intervention administration, and
  • has agreed to continue adequate contraception during the entire study treatment period.

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

Medical conditions

• Current or previous, confirmed or suspected disease caused by N. meningitidis.
• Known exposure to an individual with laboratory confirmed N. meningitidis infection, within 60 days prior to enrollment.
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the study intervention.
• Medical conditions representing a contraindication to intramuscular vaccination and blood draws.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).
• Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the study.

Prior/Concomitant therapy

• Use of any investigational or non-registered product (drug, vaccine or medical device) other than the study intervention during the period beginning 30 days before the first dose of study intervention (Day -29 to Day 1), or their planned use during the study period.

• Chronic administration of immune-modifying drugs (defined as more than 14 consecutive days in total) and/or planned use of long-acting immune-modifying treatments at any time up to the end of the study.

  • Within 90 days prior to study intervention administration: for corticosteroids, this will mean prednisone equivalent ≥20 mg/day for adult participants or >= 0.5 mg/kg/day with maximum of 20 milligram (mg)/day for pediatric participants. Inhaled and topical steroids are allowed.
  • Within 90 days prior to study intervention administration: long-acting immune-modifying drugs including among others immunotherapy (e.g., TNF-inhibitors), monoclonal antibodies, antitumoral medication.

• Administration of immunoglobulins and/or any blood products or plasma derivatives within 180 days prior to study intervention administration and/or planned use at any time up to the end of the study.

For primed group only:

• Participants who received additional dose(s) of group B meningococcal vaccine other than 2+1 or 3+1 schedule prior to study intervention administration.

Prior/Concurrent clinical study experience

• Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non-investigational intervention (drug/vaccine/invasive medical device).

Other exclusion criteria

• Pregnant or lactating female participant.
• Any study personnel or their immediate dependents, family, or household member.
• Child in care.

Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/About\_GSK\_Patient\_Level\_Data\_Sharing\_Final\_13July2023.pdf

Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or asset(s) with development terminated across all indications.

Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months, but an extension may be granted, when justified, for up to 6 months.

This is an Open-Label study.