WASHINGTON: An experimental oral vaccine against Shigella, a bacterium that causes severe intestinal infections, demonstrated 89% effectiveness in a Phase 2 clinical trial, offering hope for preventing a disease that affects millions of people worldwide.
The findings, published in the journal The Lancet Infectious Diseases, are based on a study involving 73 healthy adults between the ages of 18 and 49 at two clinical research centers in the United States.
Participants received either the experimental vaccine, known as WRS2, or a placebo. The live, weakened oral vaccine was developed to protect against Shigella sonnei, one of four species of the Shigella bacterium.
Shigella infections can cause diarrhea, vomiting and severe intestinal illness. Health experts have warned that some strains are becoming increasingly resistant to commonly used antibiotics, and there is currently no approved vaccine against the disease.
Among the 34 participants who received two doses of the vaccine, three (9%) developed shigellosis, compared with 21 of 26 participants (81%) who received the placebo.
Researchers reported an overall vaccine efficacy of 89% and found that recipients developed a strong immune response.
Most side effects were mild, although six participants experienced more severe reactions. After reviewing the safety data, an independent monitoring board recommended reducing the vaccine dose in future studies.
Lead researcher Dr Robert W Frenck Jr said the results represent an important step toward developing a safe and effective vaccine against Shigella.
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Researchers plan to determine the optimal dose in the next phase of testing and conduct larger trials, including in African countries where children bear a significant burden of the disease.
