Mosquirix™ (RTS,S/AS01e) Malaria Vaccine Clinical Trials, Dosage, Efficacy, Indication, Side Effects
GSK's Mosquirix™ RTS,S/AS01e (RTS,S) is a recombinant malaria vaccine with the P. falciparum circumsporozoite protein (CSP) from the pre-erythrocytic stage. Mosquirix triggers the immune system to defend against the first stages when the Plasmodium falciparum malaria parasite enters the human host's bloodstream through a mosquito bite and infects liver cells. The T-cell epitope of CSP is O-fucosylated in Plasmodium falciparum and Plasmodium vivax, while the RTS,S malaria vaccine produced in yeast is not. The vaccine prevents the parasite from infecting the liver, entering the bloodstream, infecting red blood cells, and leading to disease symptoms. Additionally, due to the vaccine's composition, it protects against the hepatitis B virus; however, it should not be used solely for this purpose.
In July 2015, the European Medicines Agency (EMA) issued a positive regulatory assessment EMEA/H/W/002300/001 of the RTS,S malaria vaccine for 5–17-month-olds, which was updated on July 31, 2020. The EMA updated the scientific information in July 2023. The EMA stated that this malaria vaccine should be used in areas where the Plasmodium falciparum parasite is responsible for causing malaria.
The World Health Organization (WHO) and Malaria Policy Advisory Group (MPAG) recommend the widespread use of the RTS, S/AS01 malaria vaccine among children in sub-Saharan Africa. GSK confirmed that the WHO awarded prequalification to Mosquirix (RTS,S) on September 6, 2022, the first WHO prequalification for a malaria vaccine. The WHO prequalification is a mandatory prerequisite for United Nations agencies, such as UNICEF, to procure the vaccine in partnership with Gavi, the Vaccine Alliance, and eligible countries. The WHO announced the World Malaria Report 2022 on December 8, 2022. In March 2022, a new WHO position paper was published. The WHO posted updated FAQs in July 2023. The WHO's Strategic Advisory Group of Experts (SAGE) updated its recommendations on the malaria vaccine in September 2023. About 1.5 million African children have received the vaccine through a WHO-coordinated pilot program.
In November 2023, Gavi reported data from the evaluation of the pilot introduction of the RTS,S/AS01 malaria vaccine, showing a 13% reduction in mortality from all causes among children eligible for vaccination. The RTS/S vaccine also led to a 22% reduction in hospitalizations for severe clinical malaria. As of June 25, 2025, with Gavi support, RTS,S is expected to be rolled out in 12 African endemic countries through routine immunisation programmes by the end of 2025.
On November 6, 2025, The Lancet Global Health published results from a phase 4 clinical trial, which concluded that over 1 year of follow-up after the third vaccine dose, vaccination with RTS,S/AS01E in real-world settings showed significant reductions in malaria burden. These findings reinforce the continued use of RTS,S/AS01E vaccination in children as an effective public health measure to reduce malaria-related illness and mortality in endemic regions, and highlight its relevance for future malaria control strategies.
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Mosquirix RTS,S/AS01 Vaccine Availability 2025
As of June 2025, 18 African countries, including Cameroon, Malawi, Kenya, Sierra Leone, and Ghana, have introduced the vaccine into their routine immunization programs. African countries are set to receive 18 million doses over the next two years. The Mosquirix malaria vaccine is not available in the U.S.
Mosquirix RTS,S/AS01 Vaccine Price
On June 25, 2025, Bharat Biotech International Limited and GSK plc announced that Bharat Biotech will reduce the price of RTS,S by more than half, to less than $5, progressively by 2028.
Mosquirix RTS,S/AS01 Vaccine United States
The U.S. Centers for Disease Control and Prevention (CDC) published "Malaria Vaccines: The Way Forward" on October 7, 2021, in collaboration with the Kenya Medical Research Institute. The CDC led the RTS,S/AS01 clinical trial at one site in western Kenya. While the studies are ongoing, sufficient safety and efficacy data have been collected to support a broader recommendation for the RTS,S/AS01 vaccine.
Mosquirix RTS,S/AS01 Vaccine History
GSK developed the RTS,S malaria vaccine over the course of 30 years. The RTS,S vaccine was developed in 1987 as part of a collaboration between GlaxoSmithKline and the Walter Reed Army Institute of Research, which began in 1984.
Mosquirix RTS,S/AS01 Vaccine Indication
On October 6, 2020, the WHO recommended widespread use of the RTS,S/AS01 (RTS,S) malaria vaccine among children in sub-Saharan Africa and other regions with moderate to high P. falciparum malaria transmission. In Europe, Mosquirix is currently indicated for children aged 5 to 17 months and infants aged 6 to 12 weeks at the time of the first vaccination, to help protect against malaria caused by the Plasmodium falciparum parasite. However, Mosquirix is not approved for use in older children, teenagers, or adults.
Mosquirix RTS,S/AS01 Dosage
Mosquirix is administered as an intramuscular injection. The WHO recommends that the RTS,S malaria vaccine be administered in four doses to children aged 5 months and above to reduce the disease burden and malaria incidence. On March 28, 2023, the WHO stated that SAGE recommends flexibility in the immunization schedule and supports reducing the minimum interval between doses 3 and 4 to 6 months to optimize impact.
Mosquirix RTS,S/AS01 Side Effects
The RTS,S/AS01 vaccine safety profile is similar to that of other routine childhood vaccines, except for an increased risk of febrile seizures. At first vaccination, children aged 5–17 months were more likely than controls to have a febrile seizure within seven days after vaccination, especially during the third dose. This effect was transient, and all affected children recovered after seven days. Safety surveillance also suggested a potential increased risk of meningitis and cerebral malaria in this same age group.27 A study in Kenyan children with WHO Stage 1 or 2 HIV disease found that RTS,S/AS01 was well-tolerated in this population and can be safely included in future vaccination programs. The EMA published a Summary of the risk management plan for Mosquirix on July 31, 2020.
RTS, S/AS01E Vaccination with Malaria Chemoprevention
A study published in The Lancet Infectious Diseases in August 2023 confirms that the benefits of combining the RTS, S/AS01E (RTS,S) malaria vaccine with antimalarial drugs (sulphadoxine-pyrimethamine and amodiaquine) reduced clinical malaria episodes, including cases of severe malaria and deaths from malaria in young children by nearly two-thirds (57·7% (53·3 to 61·7) and versus RTS/AS01E-alone being 59·0% (54·7 to 62·8) compared with either RTS, S vaccination or seasonal malaria chemoprevention alone.
Mosquirix RTS, S/AS01 News
November 6, 2025 - Effectiveness of the RTS,S/AS01E malaria vaccine in a real-world setting over 1 year of follow-up after the three-dose primary schedule: an interim analysis of a phase 4 study in Ghana, Kenya, and Malawi was published.
March 7, 2025 - Dr. Aceng commented, "The malaria vaccine introduction in Uganda is a historic step forward in our fight against this deadly disease. With the support of Gavi, UNICEF, and other partners, we ensure that every eligible child has access to this life-saving intervention."
May 6, 2024—The Lancet published a commentary on asymptomatic parasitemia and the efficacy of the RTS,S vaccine. Genotyping results indicated that RTS,S can block infections before the parasite reaches the blood stage. Notably, there was no difference in protective efficacy when comparing head-to-head the RTS,S dosing regimens.
January 9, 2024 - "The selected vaccine, Mosquirix RTS, has been chosen by the country (Cameroon) based on its prequalification, ensuring guaranteed quality, efficacy, and safety for its inclusion in the vaccination programs."
August 22, 2023 - LSHTM Professor Brian Greenwood, MD, a member of the research team, said, "In addition to the study's findings—which by themselves are remarkable—we can say that children who received the RTS,S combination, and also used bednets likely had greater than 90% protection against malaria episodes during the study."
March 28, 2023 - The WHO stated: Introducing the RTS, S malaria vaccine has substantially reduced severe malaria and all-cause mortality among age-eligible children.
April 21, 2022 - The WHO announced more than 1 million children in Ghana, Kenya, and Malawi have received one or more doses of the RTS, S/AS01 (RTS, S) vaccine.
September 9, 2021 - The NEJM journal published an ORIGINAL ARTICLE - Administration of RTS, S/AS01E was noninferior to chemoprevention in preventing uncomplicated malaria. Combining these interventions resulted in a substantially lower incidence of uncomplicated malaria, severe malaria, and death from malaria than either intervention alone.
January 27, 2021 - GSK, PATH, and Bharat Biotech (BBIL) announced a product transfer agreement for the malaria vaccine, RTS, S/AS01E. Additionally, GSK will retain the production of the adjuvant (AS01E) and supply it to BBIL.
August 23, 2017 - Original Research was published. In conclusion, the RTS, S/AS01E vaccine induces T cells of higher functional heterogeneity and polyfunctionality than previously characterized. Responses detected in memory CD4+ T cell compartments may provide correlates of RTS, S/AS01-induced immunity and duration of protection in future studies of correlates of immunity.
April 23, 2015 - The Lancet published 'The efficacy and safety of RTS, S/AS01 malaria vaccine with or without a booster dose in African infants and children. This trial is registered with ClinicalTrials.gov under the number NCT00866619.
Mosquirix Clinical Trials
The Phase III efficacy and safety trial of RTS, S showed that the vaccine candidate could provide meaningful public health benefits by reducing the burden of malaria.
On August 22, 2023, The Lancet Infectious Diseases published a study that confirms the benefits of combining the RTS,S/AS01E vaccine with antimalarial drugs (sulfadoxine, pyrimethamine, and amodiaquine) to reduce clinical malaria episodes, including cases of severe malaria, and deaths from malaria in young children by nearly two-thirds compared with either RTS,S vaccination or seasonal malaria chemoprevention alone. In April 2024, The Lancet published the results of a study and a related editorial. In the first two years of RTS,S implementation, the three primary doses were effectively delivered in three African countries. No safety issues were observed in the Phase 3 trial, and the introduction of the vaccine was associated with substantial reductions in hospital admissions for severe malaria. On May 6, 2024, The Lancet published results from a phase 3 study that concluded all tested dosing regimens. Improved vaccine efficacy in participants infected during vaccination could suggest new strategies for developing and implementing highly efficacious malaria vaccines.
The Lancet published results from a study in April 2024, among children eligible to have received at least one dose of RTS,S, there was no evidence of an excess of meningitis or cerebral malaria cases in implementation areas compared with comparison areas (hospital admission with meningitis: IRR 0·63 [95% CI 0·22–1·79]; hospital admission with cerebral malaria: IRR 1·03 [95% CI 0·61–1·74]).
The NEJM published the results of a phase 3 clinical study sponsored by the London School of Hygiene and Tropical Medicine on September 9, 2021, which concluded that the administration of RTS, S was noninferior to chemoprevention in preventing uncomplicated malaria. However, combining these interventions resulted in a substantially lower incidence of uncomplicated malaria, severe malaria, and death from malaria than either intervention alone.
Clinical Trial NCT03806465: An Evaluation of the Cluster-randomised Pilot Implementation of RTS, S/AS01 Through Routine Health Systems in Moderate to High Malaria Transmission Settings in Africa.
Clinical Trial: NCT04661579: The proposed trial design has been developed to answer several questions about nature. The S vaccine efficacy in African adults may be influenced by concurrent and/or past P. falciparum infection and late immunologic hypo-responsiveness. The proposed study design encompasses five groups. Three groups (Groups 1, 2, and 3) will be administered RTS, S/AS01E on a 0-, 1-, and 7-month schedule, with Dose 3 delivered as a 1/5th fractional dose. Two groups (Groups 4 and 5) will receive a comparator vaccine at 0, 1, and 7 months.
Clinical Trial NCT03143218: A double-blind, individual randomized phase 3 trial will be undertaken in 6000 children under the age of five years living in areas of Burkina Faso or Mali where the transmission of malaria is intense and highly seasonal to determine whether the malaria vaccine RTS, S/AS01 is (a) as effective as SMC with SP + AQ in preventing clinical malaria (b) provides additional, applicable protection when given together with SMC. The primary trial endpoint will be the incidence of clinical malaria episodes detected through passive case detection. The protective efficacy of the combination compared with the vaccine alone against these outcomes was 59.6% (95% CI, 54.7-64.0), 70.6% (95% CI, 42.3-85.0), and 75.3% (95% CI, 12.5-93.0), respectively.