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The Oxford-led study demonstrated that an oral live-attenuated vaccine, CVD 1902, provided significant protection against S. Paratyphi A infection in healthy adults using a controlled human infection model, without any safety concerns.
Enteric fever, caused by Salmonella Typhi and Salmonella Paratyphi, leads to more than 100,000 deaths and over 8 million disability-adjusted life years each year. Around 30% of cases, over 2 million annually, are caused by S. Paratyphi A, for which no vaccine is currently available.
The phase 2b randomised, double-blind, placebo-controlled trial, conducted by the Oxford Vaccine Group (Department of Paediatrics, University of Oxford) at six UK sites, enrolled 72 healthy adult volunteers aged 18 to 55.
Participants received two oral doses of the CVD 1902 vaccine or a placebo, given 14 days apart. Four weeks after the second dose, they were deliberately exposed to S. Paratyphi A under carefully monitored conditions to assess protection.
Within 14 days of challenge, 21% of participants in the vaccine group and 75% in the placebo group were diagnosed with infection, equating to a vaccine efficacy of 73% (95% CI, 46–86).
No vaccine-related serious adverse events were identified, and side effects were generally mild to moderate in both groups.
Read the full story on the University of Oxford website.