Malaria vaccine

Malaria vaccine is a vaccine that is used to prevent malaria. The only approved vaccine as of 2015 is RTS,S, known by the trade name Mosquirix. It requires four injections, and has a relatively low efficacy. Due to this low efficacy, the World Health Organization (WHO) does not recommend the routine use of the RTS,S vaccine in babies between 6 and 12 weeks of age. Malaria vaccine is a vaccine that is used to prevent malaria. The only approved vaccine as of 2015 is RTS,S, known by the trade name Mosquirix. It requires four injections, and has a relatively low efficacy. Due to this low efficacy, the World Health Organization (WHO) does not recommend the routine use of the RTS,S vaccine in babies between 6 and 12 weeks of age. A WHO-led implementation program is piloting the vaccine in three high-malaria countries in Africa in 2019. The first phase of the project, covered by grants from Unitaid, Gavi and the Global Fund, is planned to establish the feasibility, impact and safety of RTS,S, when used as part of a routine immunization program. Research continues into recombinant protein and attenuated whole organism vaccines. RTS,S (developed by PATH Malaria Vaccine Initiative (MVI) and GlaxoSmithKline (GSK) with support from the Bill and Melinda Gates Foundation) is the most recently developed recombinant vaccine. It consists of the P. falciparum circumsporozoite protein (CSP) from the pre-erythrocytic stage. The CSP antigen causes the production of antibodies capable of preventing the invasion of hepatocytes and additionally elicits a cellular response enabling the destruction of infected hepatocytes. The CSP vaccine presented problems in trials due to its poor immunogenicity. RTS,S attempted to avoid these by fusing the protein with a surface antigen from hepatitis B, hence creating a more potent and immunogenic vaccine. When tested in trials an emulsion of oil in water and the added adjuvants of monophosphoryl A and QS21 (SBAS2), the vaccine gave protective immunity to 7 out of 8 volunteers when challenged with P. falciparum. RTS,S/AS01 (commercial name Mosquirix), was engineered using genes from the outer protein of P. falciparum malaria parasite and a portion of a hepatitis B virus plus a chemical adjuvant to boost the immune response. Infection is prevented by inducing high antibody titers that block the parasite from infecting the liver. In November 2012 a Phase III trial of RTS,S found that it provided modest protection against both clinical and severe malaria in young infants. As of October 2013 preliminary results of a phase III clinical trial indicated that RTS,S/AS01 reduced the number of cases among young children by almost 50 percent and among infants by around 25 percent. The study ended in 2014. The effects of a booster dose were positive, even though overall efficacy seem to wane with time. After four years reductions were 36 percent for children who received three shots and a booster dose. Missing the booster dose reduced the efficacy against severe malaria to a negligible effect. The vaccine was shown to be less effective for infants. Three doses of vaccine plus a booster reduced the risk of clinical episodes by 26 percent over three years, but offered no significant protection against severe malaria. In a bid to accommodate a larger group and guarantee a sustained availability for the general public, GSK applied for a marketing license with the European Medicines Agency (EMA) in July 2014. GSK treated the project as a non-profit initiative, with most funding coming from the Gates Foundation, a major contributor to malaria eradication. On 24 July 2015, Mosquirix received a positive opinion from the EMA on the proposal of the vaccine to be used to vaccinate children aged 6 weeks to 17 months outside the European Union.