ACT-CHIK

The challenge

Spread by mosquitoes, the chikungunya virus causes a variety of debilitating symptoms, including fever, headache, joint pain, and fatigue. In some cases, symptoms can be severe and have long-term musculoskeletal and neurological complications, especially in children. 

Chikungunya is now endemic in multiple countries and can also trigger large-scale outbreaks. Given the number of other illnesses that present symptoms like chikungunya, it is almost certainly being under-diagnosed and under-reported in sub-Saharan Africa. It is already having major health and economic impacts on households and health systems in the region, and these are likely to worsen as climate change accelerates the virus's spread.

Two vaccines have been licensed for chikungunya. However, one (IXCHIQ®) had its license suspended by the US Food and Drug Administration (FDA) in 2025 due to safety concerns, and the company withdrew its dossier in the US in Jan 2026, while a second (Vimkunya®) is not licensed for children under 12 years of age.

The project

The ACT-CHIK project is evaluating a potential alternative vaccine with several advantageous features. Measles-vectored chikungunya vaccine (MV-CHIK), developed by Institut Pasteur in Paris, uses a measles virus backbone, which is highly immunogenic in animal models, to deliver chikungunya antigens. It is available as a convenient, highly stable freeze-dried (lyophilised) formulation.

Six phase I and II trials of MV-CHIK have been carried out in Europe and the US, including a safety and immunogenicity study in a chikungunya-endemic country (Puerto Rico). No safety concerns have been identified, and the vaccine shows a promising immunogenicity profile. Given that chikungunya outbreaks are unpredictable and occur with little warning, it is difficult to carry out a conventional clinical trial to assess a vaccine’s protective efficacy. However, neutralising antibody levels are considered an acceptable surrogate for protection and can be used to infer likely clinical efficacy.

 The ACT-CHIK project has three key goals:

• To generate safety and immunogenicity data in African populations, through a phase Ib/III trial in a mix of chikungunya endemic and non-endemic settings. Since the vaccine has not been tried in Africans, the trial will first assess safety in different age groups, including children, before progressing to a large-scale immunogenicity and safety study. The clinical trials will be implemented by the University of Rwanda (UR - Rwanda), Kenya Medical Research Institution (KEMRI – Kenya), IRRUA Specialist Teaching Hospital Board of Management (IRRUA – Nigeria) and Institut Pasteur de Dakar (IPD – Senegal).
• To prepare for technology transfer to enable MV-CHIK to be manufactured in sub-Saharan Africa, at the IPD, sub-Saharan Africa’s only WHO-prequalified vaccine manufacturer. A Brazilian manufacturer with experience in vaccine manufacturing, Fiocruz, will carry out a feasibility study and identify what is required to enable IPD to produce the vaccine commercially, in collaboration with Institut Pasteur.
• To develop a regulatory strategy for licensure of MV-CHIK vaccine in Africa.

Impact

The ACT-CHIK project has the potential to deliver significant health and economic benefits to sub-Saharan Africa. It will:

• Demonstrate whether MV-CHIK is safe for use in African adults, adolescents, and children and is sufficiently immunogenic to likely protect against the chikungunya virus.
• Establish a roadmap for technology transfer so that MV-CHIK can ultimately be manufactured in sub-Saharan Africa.
• Identify a regulatory pathway to ensure rapid approval and introductions should positive results be obtained in the trial.
• Contribute to Africa’s strategic objective to manufacture 60% of its vaccine needs by 2040.

In addition to its health benefits, an effective vaccine against chikungunya would have multiple economic advantages: protecting households against loss of earnings and healthcare costs, reducing national healthcare costs, and preventing economic losses from people having to take time off work.