A completely effective vaccine is not yet available for malaria, although several vaccines are under development. SPf66 was tested extensively in endemic areas in the 1990s, but clinical trials showed it to be insufficiently effective. Other vaccine candidates, targeting the blood-stage of the malaria parasite's life cycle, have also been insufficient on their own. RTS,S is one of several potential vaccines under development that target the pre-erythrocytic stage of the disease. Among them, RTS,S has shown the most promising results so far.
The RTS,S vaccine was engineered using genes from the repeat and T-cell epitope in the circumsporozoite protein (CSP) of Plasmodium falciparum malaria parasite and a viral envelope protein of the hepatitis B virus (HBsAg) and a chemical adjuvant to boost the immune system response. Infection is prevented by inducing high antibody titers that block the parasite from infecting the liver.
The RTS,S-based vaccine formulation had previously been demonstrated to be safe, well tolerated, immunogenic, and to potentially confer partial efficacy in both malaria-naive and -experienced adults as well as children, further research was considered necessary to improve the effectiveness of the vaccine.
In November 2012, findings from a Phase III trial of RTS,S reported that it provided modest protection against both clinical and severe malaria in young infants. In October 2013, GlaxoSmithKline (GSK) reported that the RTS,S vaccine reduced the amount of cases amongst young children by almost 50 percent and among infants by around 25 percent, following the conclusion of an 18-month clinical trial. GlaxoSmithKline is set to submit an application for a marketing license with the European Medicines Agency (EMA) in 2014. The new vaccine has the backing of the UN’s Swiss-based WHO which states that it will recommend the use of RTS,S for use starting in 2015, providing it gets approval.
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