ETVAX Oral Vaccine Shows Promise Against Deadly E. Coli Infections in Children
Key Insights
ETVAX demonstrated up to 80.6% effectiveness against enterotoxigenic E. coli (ETEC (search)) diarrhea (search) in children without intestinal parasites, marking the first oral ETEC vaccine to show real protection in high-burden settings.
The Phase IIb trial in Gambia enrolled 4,936 children aged 6-18 months and found 67.8% protection in infants who started vaccination before nine months of age.
While missing its primary endpoint with 26.6% efficacy, ETVAX showed 48.2% effectiveness against ETEC (search) regardless of co-infections and reduced all-cause moderate-to-severe diarrhea (search) by 21%.
A novel oral vaccine called ETVAX has demonstrated significant potential to protect children against deadly enterotoxigenic Escherichia coli (search) (ETEC (search)) infections, showing up to 80.6% effectiveness in preventing moderate-to-severe diarrhea (search) in a landmark Phase IIb trial conducted in Gambia. The results, published in The Lancet Infectious Diseases, represent the first time an oral ETEC vaccine has shown real protection in a high-burden, low-income setting.
Trial Design and Population
The EDCTP2-funded trial enrolled 4,936 children aged six to 18 months, with participants randomized to receive three doses of either ETVAX or placebo at days 1, 15, and 90. The study was coordinated by Scandinavian Biopharma (search) and followed children over two years to evaluate vaccine efficacy and safety.
ETEC (search) bacteria are the most common cause of travelers' diarrhea (search) and frequently cause childhood diarrhea in low-income regions. In children below age five, whose immune systems are still developing, these infections can lead to malnutrition (search) and cause up to 42,000 deaths annually. The bacteria use "adhesin" proteins to attach to intestinal mucosa before releasing toxins (search) that cause watery diarrhea and abdominal cramping.
Vaccine Composition and Mechanism
ETVAX addresses the complexity of ETEC (search) bacteria, which have 26 distinct adhesin proteins (search) and two kinds of toxins (search). The research team, led by immunologist Ann-Mari Svennerholm of the University of Gothenburg in Sweden, created a formula using the four most common adhesin proteins found on 80 percent of all enterotoxigenic E. coli. They combined these proteins with an inert part of a toxin and a component that stimulates intestinal immune responses.
"At present, there is no approved E. coli vaccine available for protection against any type of E. coli infections in humans," Svennerholm noted, emphasizing that ETVAX is the first to show significant protection against E. coli infections in people.
Efficacy Results and Age-Dependent Protection
While ETVAX did not meet its primary endpoint, demonstrating 26.6% efficacy (p=0.43) against ETEC (search)-positive diarrhea (search) in children without co-infections, it showed more promising results in secondary analyses. The vaccine demonstrated 48.2% effectiveness (p=0.053) against ETEC regardless of co-pathogens, narrowly missing statistical significance.
Most notably, ETVAX showed 80.6% effectiveness (p=0.0092) in children who were not infected with certain intestinal parasites. The study also highlighted the importance of early vaccination, with 67.8% of children who started receiving the vaccine before nine months of age being protected against ETEC (search)-positive diarrhea (search).
Thomas Wierzba, corresponding author and professor of infectious diseases at Wake Forest School of Medicine, explained that ETVAX reduced moderate-to-severe diarrhea (search) from viruses, bacteria, or other parasites by 21 percent, suggesting the vaccine provides partial protection against multiple gut pathogens.
Cross-Protection Against Other Pathogens
When researchers included co-infections from common gut pathogens such as Shigella, Cryptosporidium, rotavirus, or norovirus, ETVAX reduced moderate-to-severe diarrhea (search) from ETEC (search) by 48 percent in all children and by 68 percent in infants younger than nine months. This cross-protection highlights the vaccine's potential broader impact on childhood diarrheal diseases.
David Sack, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health who was not involved in the study, called it a "high-quality study" because it used different outcomes to evaluate the vaccine. However, he noted that the mechanisms behind cross-protection against other pathogens require further investigation.
Safety Profile
The vaccine demonstrated a favorable safety profile comparable to placebo. Serious adverse events occurred in 1% (24) of children in the ETVAX group and 1.3% (32) in the placebo group, with none of the serious adverse events related to the vaccine. ETVAX increased antibodies against multiple ETEC (search) adhesin proteins (search), especially after the third dose.
Regulatory Pathway and Future Development
Following these generally positive results, the European Medicines Agency has approved progression to a pivotal Phase III trial, which will enroll 5,800 infants between six and nine months of age from low- and middle-income countries. This trial will test the vaccine's consistency across different populations.
If ETVAX secures regulatory approval, it would become the first vaccine available to protect against ETEC (search)-prompted diarrhea (search), joining existing vaccines like MSD's RotaTeq and GSK's Rotarix in the preventative arsenal against childhood diarrheal diseases. UNICEF commonly provides children in low-to-middle income countries with rotavirus vaccines.
The development comes as other companies pursue similar goals, with Moderna evaluating its trivalent, mRNA-based norovirus vaccine mRNA-1403 in a Phase III trial that began dosing in 2024. The EDCTP3 hopes that ETVAX will become an important addition to the all-cause diarrhea (search) treatment arsenal, particularly in low-income areas where lack of access to sanitation and clean drinking water increases the risk of E. coli infections.