Mosquirix

Mosquirix, also known by its development name RTS,S/AS01, is a malaria vaccine designed to protect against Plasmodium falciparum malaria, the most deadly malaria parasite. It was developed by GlaxoSmithKline (GSK) in collaboration with PATH, with support from international health partners and funders. The vaccine is intended for young children in regions with moderate to high transmission, primarily in sub-Saharan Africa, and has been approved for use in other malaria-endemic areas under specific regulatory and programmatic conditions.

Mechanism and composition: Mosquirix is a recombinant vaccine that combines a segment of the circumsporozoite protein from P. falciparum with hepatitis B surface antigen to form virus-like particles, formulated with the AS01 adjuvant. The immune response aims to reduce parasite development in the liver after a mosquito bite, thereby lowering the risk of clinical malaria and severe disease.

Clinical development and regulatory status: In Phase III trials, Mosquirix demonstrated partial protection, reducing episodes of clinical malaria by a modest amount in the target age group, with protection generally waning over time. It remains the first malaria vaccine to reach large-scale evaluation in real-world settings. The European Medicines Agency approved it in 2015, and the World Health Organization subsequently endorsed pilot introduction in Ghana, Kenya, and Malawi beginning in 2019, with broader policy and deployment decisions made in the following years. Financing and distribution involve global health partners such as Gavi, UNICEF, WHO, and national immunization programs.

Usage and dosing: The recommended schedule consists of a four-dose primary series for infants aged 5–17 months, given at 5, 6, and 7 months, and a fourth dose at 18 months. Mosquirix is intended to be used alongside other malaria control measures, including bed nets and vector control, rather than as a standalone solution.

Impact and limitations: Mosquirix offers partial protection and reduces malaria episodes and, to some extent, severe disease, but it does not provide complete immunity. Ongoing surveillance, integration with public health strategies, and sustained funding are essential for maximizing its impact.