Study to Assess a Booster Dose of GBS-NN/NN2 Vaccine

Inclusion Criteria

To be confirmed at Screening:

• Women who have participated in study MVX0002, with GBS-NN/NN2 vaccine and received active vaccine or placebo (unless it is necessary to recruit vaccine naïve participants to bolster the number of participants who received placebo in MVX0002).
• Able to voluntarily provide written informed consent to participate in the study.
• Healthy female participants aged 18-40 years (vaccine naïve participants only).
• Female participant of childbearing potential willing to use a highly effective method of contraception (in addition to a condom for male partners), if applicable (unless of non-childbearing potential or where abstaining from sexual intercourse is in line with the preferred and usual lifestyle of the participant) from the first dose until completion of the Day 85 visit. A woman is considered of childbearing potential, i.e. fertile, following menarche and until becoming post-menopausal unless permanently sterile. Permanent sterilisation methods include hysterectomy, bilateral salpingectomy and bilateral oophorectomy. For the purposes of this study, this definition of a female of childbearing potential applies to all females in the study i.e., those who participated in the MVX0002 study and those who are considered vaccine naïve.
• Female participant of non-childbearing potential. For the purposes of this study, this is defined as the participant being at least 4 months post-surgical sterilisation (including bilateral fallopian tube ligation or bilateral oophorectomy with or without hysterectomy).
• Female participant with a negative pregnancy test at Screening and prior to dose.
• Female participant of menopausal status confirmed by demonstrating at Screening that the serum level of the follicle stimulating hormone (FSH) falls within the respective pathology reference range. In the event a participant's menopausal status has been clearly established (for example, the participant indicates she has been amenorrhoeic for 10 years, confirmed by medical history, etc), but serum FSH levels are not consistent with a postmenopausal status, determination of the participant's eligibility to be included in the study will be at the Investigator's discretion following consultation with the Sponsor.
• Body mass index (BMI) ≥18 and ≤30 kg/m2 (vaccine naïve participants only).
• Participants' weight ≥ 50 kg and ≤ 100 kg at Screening (vaccine naïve participants only).
• Non-smokers for at least 3 months prior to study vaccine administration.
• No clinically significant abnormal test results for serum biochemistry, haematology and/or urine analyses within 28 days before dose administration of the IMP.
• Participants with a negative urinary drugs of abuse (DOA) screen (including alcohol) test results, determined within 28 days before dose administration of the IMP (N.B.: A positive test result may be repeated at the Investigator's discretion, if on prescribed opiates resulting in a positive test, participants may be eligible at the investigators discretion).
• No clinically significant abnormalities in vital signs (supine blood pressure/heart rate, respiration rate, tympanic temperature) determined within 28 days before dose of IMP.
• Participants with a negative coronavirus (COVID-19) Reverse Transcription Polymerase Chain Reaction (RT-PCR) test on admission (Day 1 or Day-1 if deemed appropriate by the Principal Investigator (PI)) if required at the time.

To be re-confirmed prior to dose administration:

• Participants continue to meet all screening inclusion criteria.
• Participants with a negative urinary drugs of abuse screen (including alcohol) prior to dose administration.
• Participants with a negative pregnancy test.
• Participants with a negative COVID-19 RT-PCR test on admission (Day 1) (or Day -1 if deemed appropriate by the PI) if required at the time.

Exclusion Criteria

To be confirmed at Screening:

• Participants who have an autoimmune disease.
• P