Promising New Vaccine Targets Typhoid and Salmonella Infections in First Human Trial

Researchers from the University of Maryland School of Medicine have announced the successful completion of a Phase I clinical trial for a groundbreaking vaccine designed to combat both typhoid fever and invasive non-typhoidal Salmonella infections. These diseases are significant health threats, especially among children in sub-Saharan Africa where they account for substantial illness and mortality.

The novel vaccine, known as the Trivalent Salmonella Conjugate Vaccine (TSCV), is built using sugar molecules derived from the outer coating of Salmonella typhi bacteria—which causes typhoid—and the two most common types of invasive Salmonella not linked to typhoid. These sugars are attached to special proteins to enhance the immune system's ability to recognize and fight the bacteria.

In the trial, 22 healthy adults in the United States were administered either a low dose (6.25 µg), a high dose (12.5 µg), or a placebo. Results demonstrated that the vaccine was safe and well-tolerated, with only mild, transient pain at the injection site. Notably, all vaccinated participants developed strong immune responses to all three bacterial components, whereas the placebo group showed no such response.

The primary scientist behind the study, Dr. Wilbur Chen, expressed optimism, stating, "These results are highly promising and suggest that TSCV has the potential to provide protection for children in regions where typhoid and Salmonella infections are endemic and deadly."

Aside from its benefits in developing countries, the vaccine could also help reduce Salmonella infections in the United States, where contaminated food products—such as chicken, eggs, and produce—cause over 1.35 million infections annually, resulting in more than 26,000 hospitalizations. The vaccine targets the most common serotypes responsible for these infections.

Interestingly, some adult trial participants showed preexisting antibodies, indicating prior exposure to the bacteria possibly through foodborne illness. Such immune priming might strengthen and prolong protection, especially in adults. The vaccine also induced a balanced immune response, including long-lasting antibodies and activation of white blood cells crucial for disease defense, suggesting it could offer both intestinal and systemic protection.

The development was a collaboration with Bharat Biotech International Limited, leveraging their WHO-prequalified Typbar TCV platform. Experts highlight that in 2017, sub-Saharan Africa experienced over 420,000 cases and 66,000 deaths due to Salmonella, with typhoid causing an additional 650,000 cases and nearly 9,000 fatalities. A single vaccine offering protection against both diseases could dramatically improve pediatric health outcomes worldwide.

Future studies are planned to evaluate the vaccine's effectiveness in young children and to explore immune responses that correlate with protection, aiming to extend benefits to the most vulnerable populations.