This is an open label booster vaccine follow-up study. Participants who had received a primary course of GBS-NN/NN2 or placebo in Study MVX0002 will be invited to return to receive a booster dose (or first dose in the case of placebo or vaccine naïve participants) 1 to 5 years after the completion of the primary course of vaccination. All participants will receive a single dose of GBS-NN/NN2 containing 50μg of each fusion protein.

This is an open label vaccine booster follow-up study. Participants who had received a primary course of GBS-NN/NN2 or placebo in Study MVX0002 will be invited to return to receive a booster dose (or first dose in the case of placebo or vaccine naïve participants) 1 to 5 years after the completion of the primary course of vaccination. All participants will receive a single dose of GBS-NN/NN2 containing 50μg of each fusion protein.

A minimum of 30 and a maximum of 40 female participants will be recruited, comprised of between 20 and 30 participants who had received previous vaccination with GBS-NN/NN2 in the MVX0002 study and up to 10 participants who had received placebo in the MVX0002 study. If an insufficient number of participants (less than 5) who previously received placebo return to this study, vaccine naïve participants will be recruited.

The study will include 7 visits: Visit 1 (Screening), Visit 2 (Day 1 dosing), Visit 3 (Day 8), Visit 4 (Day 29), Visit 5 (Day 57), Visit 6 (Day 85) and Visit 7 (Day 183 Follow-up).

Inclusion Criteria:

To be confirmed at Screening:

1. 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).
2. Able to voluntarily provide written informed consent to participate in the study.
3. Healthy female participants aged 18-40 years (vaccine naïve participants only).
4. 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.
5. 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).
6. Female participant with a negative pregnancy test at Screening and prior to dose.
7. 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.
8. Body mass index (BMI) ≥18 and ≤30 kg/m2 (vaccine naïve participants only).
9. Participants' weight ≥ 50 kg and ≤ 100 kg at Screening (vaccine naïve participants only).
10. Non-smokers for at least 3 months prior to study vaccine administration.
11. No clinically significant abnormal test results for serum biochemistry, haematology and/or urine analyses within 28 days before dose administration of the IMP.
12. 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).
13. No clinically significant abnormalities in vital signs (supine blood pressure/heart rate, respiration rate, tympanic temperature) determined within 28 days before dose of IMP.
14. 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:

1. Participants continue to meet all screening inclusion criteria.
2. Participants with a negative urinary drugs of abuse screen (including alcohol) prior to dose administration.
3. Participants with a negative pregnancy test.
4. 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:

1. Participants who have an autoimmune disease.
2. Participants who have a current infection or any significant illness at Screening (such participants can be rescreened once the active infection or significant illness has resolved).
3. Participants with history or presence of significant cardiovascular disease, pulmonary, hepatic, gallbladder or biliary tract, renal, haematological, gastrointestinal, endocrine, immunologic, dermatological, neurological, psychiatric, autoimmune disease or current infection.
4. Laboratory values at Screening which are deemed by the Investigator to be clinically significantly abnormal.
5. Positive for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg) or hepatitis C virus antibody (HCV Ab).
6. Participation in a clinical drug study during the 90 days or 5 half-lives, whichever is longer, preceding the initial dose in this study (such participants can be rescreened once the 90-day or 5 half-lives period has elapsed).
7. Participants with a history of severe allergic reactions after previous vaccination.
8. Participants with a history of hypersensitivity to the Investigational Medicinal Product (IMP) or any of the excipients within the IMP or documented allergy to aminoglycosides.
9. Participants who have received any vaccine within 7 days of dosing, or who are planning to receive a vaccine up to 7 days after receiving the GBS-NN/NN2 vaccine.
10. Participants who have received immunosuppressive therapy within the 6 months prior to Screening.
11. Participants with tattoos at the proposed site of vaccine administration.
12. Participants who, in the opinion of the Investigator, are unsuitable for participation in the study.
13. Pregnant or breast feeding.
14. Current or history of drug or alcohol abuse, or a positive urine alcohol test prior to dosing (prescribed opiates are acceptable).
15. Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements within 28 days or 5 half-lives (whichever is longer) prior to the first dose of IMP with the exception of contraceptives and paracetamol (applies to vaccine naïve participants i.e., those who did not participate in the MVX0002 study and participants from the MVX0002 study (both active and placebo) who have not developed new medical conditions which require the use of chronic medications considered as permitted). If participants who participated in the MVX0002 study (either active or placebo recipients) have developed new medical conditions which require the use of chronic medications that do not affect the immune system, the inclusion of such participants will be permitted at the discretion of the Investigator on a case-by-case basis and, only if it is considered that the inclusion within the MVX0003 study will not be detrimental to participant safety.
16. Donation of blood or blood products within 90 days prior to vaccine administration.

To be re-confirmed prior to dose administration:

1. Development of any exclusion criteria since the Screening visit.
2. Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements since the Screening visit with the exception of contraceptives and paracetamol (applies to vaccine naïve participants i.e., those who did not participate in the MVX0002 study and participants from the MVX0002 study (both active and placebo) who have not developed new medical conditions which require the use of chronic medications considered as permitted).
3. Participation in a clinical study since the Screening visit.
4. Donation of blood or blood products since the Screening visit.

From screening to end of safety follow-up.

All Adverse Events (AEs) were recorded, whether considered minor or serious, drug-related, or not.

From vaccination (Day 1) to Day 7 solicited and unsolicited AEs were recorded. The following AE were solicited : Injection site reactions, fatigue, headache, myalgia and Influenza like illness.

From Day 8 to Day 85 only unsolicited AEs were collected. From Day 86 to Day 183 all AEs were recorded in the Patient Diary Card and evaluated at Visit 7.