Promising new vaccine shows strong protection against diarrhoeal diseases in young children

24 February 2026

A new vaccine candidate designed to protect against one of the world’s leading causes of diarrhoeal disease has shown highly encouraging results in a phase IIb clinical trial conducted in The Gambia. The oral vaccine, ETVAX, targets enterotoxigenic E. coli (ETEC), a common gastrointestinal pathogen that is a major cause of diarrhoeal disease in young children in low- and middle-income countries and the most common cause of travellers’ diarrhoea.

Results from the EDCTP2-funded ETEC Vaccine Efficacy project, published in The Lancet Infectious Diseases, indicate that ETVAX could significantly reduce the burden of moderate-to-severe diarrhoeal disease in infants and young children, with important implications for both short- and long-term health.

“We are proud to see this project reach such an important milestone. These results provide a critical foundation for advancing into a phase III study and, if successful, will bring us closer to delivering a much-needed new vaccine to prevent diarrhoeal disease.”

Dr Debora Bade, Project Office, EDCTP Association

A major cause of childhood illness

ETEC is one of the most significant causes of diarrhoeal disease in young children in low- and middle-income countries. While acute illness can lead to dehydration and hospitalisation, repeated infections can impact the growth and development of children, affecting their education and later earning potential, as well as their susceptibility to non-communicable diseases in later life. Effective prevention strategies, therefore, have the potential to deliver lifelong health and development benefits.

ETVAX is currently the most advanced ETEC vaccine candidate in clinical development. It is formulated to provide coverage against more than 90% of circulating ETEC strains in high-burden settings.

Large-scale phase IIb trial in The Gambia

The phase IIb study, funded by EDCTP2, assessed the safety and efficacy of ETVAX in 4,936 young children aged 6-18 months across different regions of The Gambia. In this randomised, double-blind, placebo-controlled trial, participants received a three-dose regimen of either ETVAC or placebo and were followed for up to 24 months.

Key findings include:

  • Approximately 50% vaccine efficacy against ETEC-positive moderate-to-severe diarrhoea, irrespective of co-infections
  • 81% vaccine efficacy against ETEC-positive moderate-to-severe diarrhoea when enteroparasitic co-infections were excluded
  • 68% vaccine efficacy among children vaccinated before nine months of age, highlighting the importance of early vaccination.
  • A 21% reduction in all-cause moderate-to-severe diarrhoea over the 24-month follow-up period, a level of protection comparable to the all-cause protection observed for rotavirus vaccine, which is currently administered to approximately 40 million children in low- and middle-income countries through UNICEF.

The trial also confirmed an excellent safety profile and demonstrated strong systemic immune responses against key ETEC antigens.

Ready for phase III development

Based on the accumulated safety, immunogenicity, and efficacy data, the European Medicines Agency (EMA), following formal Scientific Advice, concluded that ETVAX is ready to advance into pivotal phase III clinical development. The vaccine is now considered phase III-ready for the prevention of moderate-to-severe ETEC diarrhoea in infants and young children in low- and middle-income countries.

If phase III trials confirm these findings and regulatory approval is achieved, ETVAX could become an important new tool for reducing ETEC-related diarrhoea in high-burden settings and help prevent long-term developmental impacts associated with repeated diarrhoeal episodes in early childhood.

Publications details

Efficacy of ETVAX, a vaccine against enterotoxigenic Escherichia coli-positive diarrhoea in Gambian children: a double-blind, randomised, placebo-controlled, phase 2b trial
Hossain, M Jahangir et al.
The Lancet Infectious Diseases, Volume 0, Issue 0

More information

The ETEC Vaccine Efficacy project is funded by the EDCTP2 programme with a grant supplement from the Medical Research Council (UK Research and Innovation).