A study to evaluate the efficacy, immunogenicity and safety in a sporozoite challenge model of a fractional booster dose of GSK Biologicals' candidate malaria vaccine administered to previously vaccinated healthy malaria-naïve adults

Only for subjects from MALARIA-092 study (NCT03162614):

• Subjects vaccinated and having undergone sporozoite challenge during the primary study (MALARIA-092 [NCT03162614]). For all subjects:
• Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
• Written informed consent obtained from the subject prior to performing any study-specific procedure.
• Healthy subjects as established by medical history and clinical examination before entering into the study.
• Available to participate for the duration of the study.
• Female subjects of non-childbearing potential may be enrolled in the study.
• Female subjects of childbearing potential may be enrolled in the study, if the subject:

Has a negative pregnancy test at enrollment. For the infectivity control subjects:

• Male or female subjects between, and including, 18 and 55 years of age.

For all subjects except the infectivity control subjects:

• Any medical condition that in the judgment of the investigator would make intramuscular injection unsafe.
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine.
• History of anaphylaxis post-vaccination. For all subjects:
• Use of any investigational or non-registered product other than the study vaccine during the period starting 30 days before Day 1 (Day -29 to Day 1) (for P-Fx and NP-Fx groups)/before the malaria challenge (for infectivity control subjects), or planned use during the study period.
• Chronic administration of immunosuppressants or other immune-modifying drugs during the period starting six months prior to Day 1 (for P-Fx and NP-Fx groups) or malaria challenge (for infectivity control subjects). For corticosteroids, this will mean prednisone ≥20 mg/day, or equivalent. Inhaled and topical steroids are allowed.
• Administration of long-acting immune-modifying drugs at any time during the study period.
• Chronic use of antibiotics with anti-malarial effects.
• Planned administration/administration of a vaccine not foreseen by the study protocol in the period within seven days of Day 1 (for P-Fx and NP-Fx groups) or the malaria challenge (for infectivity control subjects).
• Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational vaccine/product.
• Seropositive for Human Immunodeficiency Virus, Hepatitis B surface antigen or Hepatitis C Virus.
• Planned travel to malaria endemic areas during the study period.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination.
• History of any reaction or hypersensitivity that would prevent the subject from utilizing all of the following: chloroquine, atovaquone/proguanil, artemether/lumefantrine.
• Current use of medications known to cause drug reactions that would prevent the subject from utilizing any of the following: chloroquine, atovaquone/proguanil, artemether/lumefantrine.
• History of severe reactions to mosquito bites.
• Acute disease and/or fever at the time of enrollment.

Subjects with a minor illness without fever may be enrolled at the discretion of the investigator.

• Hepatomegaly, right upper quadrant abdominal pain or tenderness.
• Any abnormal baseline laboratory screening tests: ALT, AST, creatinine, hemoglobin, platelet count, total WBC, out of normal range.
• Personal history of auto-immune disease.
• Administration of immunoglobulins and/or any blood products during the period starting three months before Day 1 (for P-Fx and NP-Fx groups)/the malaria challenge (for infectivity control subjects), or planned administration during the study period.
• Pregnant or lactating female.
• Female planning to become pregnant or planning to discontinue contraceptive precautions.
• History of chronic alcohol consumption and/or drug abuse.
• History of blood donation within 56 days preceding enrollment.
• Any other significant finding that in the opinion of the investigator would increase the risk of having an adverse outcome from participating in this study.
• Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination or laboratory screening tests.
• Evidence of increased cardiovascular disease risk, "moderate" or "high", according to the National Health And Nutrition Examination Survey I (NHANES I) criteria. Only for infectivity control subjects:
• Previous vaccination against malaria.
• History of splenectomy.
• Family history of congenital or hereditary immunodeficiency.
• Major congenital defects.
• Serious chronic illness.
• History of any neurological disorders or seizures.
• Diagnosed with malaria within the last 5 years (inclusive).