The efficacy was about 30% in infants 6 to 12 weeks of age and about 50% in infants 5 to 17 months of age in the first year of the trial.The RTS,S vaccine was engineered using a fusion hepatitis B surface protein containing epitopes of the outer protein of Plasmodium falciparum malaria sporozite, which is produced in yeast cells. It also contains a chemical adjuvant to boost the immune system response. The vaccine is being developed by PATH and GlaxoSmithKline (GSK), which has spent about $300 million on the project, plus about $200 million more from the Bill and Melinda Gates Foundation. Risk factors
Most adults from endemic areas have a degree of long-term infection, which tends to recur, and also possess partial immunity (resistance); the resistance reduces with time, and such adults may become susceptible to severe malaria if they have spent a significant amount of time in non-endemic areas. They are strongly recommended to take full precautions if they return to an endemic area. History
Malaria is one of the oldest known pathogens, and began having a major impact on human survival about 10,000 years ago with the birth of agriculture. The development of virulence in the parasite has been demonstrated using genomic mapping of samples from this period, confirming the emergence of genes conferring a reduced risk of developing the malaria infection. References to the disease can be found in manuscripts from ancient Egypt, India and China, illustrating its wide geographical distribution.
There is very low quality evidence indicating that doxycycline use may be associated with an increased risk of indigestion, photosensitivity, vomiting, and yeast infections, when compared with mefloquine and atovaquone-proguanil. Causal prophylaxis
Causal prophylactics target not only the blood stages of malaria, but the initial liver stage as well. This means that the user can stop taking the drug seven days after leaving the area of risk. Malarone and primaquine are the only causal prophylactics in current use. Regimens
Specific regimens are recommended by the WHO, UK HPA and CDC for prevention of P. falciparum infection. HPA and WHO advice are broadly in line with each other (although there are some differences). CDC guidance frequently contradicts HPA and WHO guidance. These regimens include:

doxycycline 100 mg once daily (started one day before travel, and continued for four weeks after returning);
mefloquine 250 mg once weekly (started two-and-a-half weeks before travel, and continued for four weeks after returning);
atovaquone/proguanil (Malarone) 1 tablet daily (started one day before travel, and continued for 1 week after returning). Can also be used for therapy in some cases.In areas where chloroquine remains effective:

chloroquine 300 mg once weekly, and proguanil 200 mg once daily (started one week before travel, and continued for four weeks after returning);
hydroxychloroquine 400 mg once weekly (started one to two weeks before travel and continued for four weeks after returning)What regimen is appropriate depends on the person who is to take the medication as well as the country or region travelled to.