No licensed vaccine, 165 million infections, and a Shigella candidate that passed its first real test

Shigellosis does not make the evening news in Europe, which is part of the problem. It is the second leading cause of fatal diarrhoeal disease worldwide, with an estimated 165 million infections a year, about 62.3 million of them in children under five, and up to 600,000 deaths¹. Treatment is mostly oral rehydration and antibiotics, and resistance is spreading. There is no licensed vaccine¹.

On Monday the French vaccine maker Valneva reported Phase 2 results for S4V2, a four-strain bioconjugate candidate; LimmaTech sponsored both trials¹. The first trial, in Kenya, gave 110 nine-month-old infants two doses at one of two dose levels, against a meningococcal control vaccine¹. Antibodies rose significantly against all four targeted Shigella serotypes compared with the control group, peaked after the second dose and were still above baseline six months later¹. Side effects were mostly mild to moderate and did not differ statistically from the control group¹.

The second trial is the more striking design. About 120 healthy adults in the United States, with no prior Shigella antibodies, received two doses or placebo a month apart and were then deliberately exposed to a strain of S. sonnei about a month later¹. The trial met its primary endpoint: a statistically significant reduction in shigellosis from that serotype in the vaccinated group¹. The release gives no efficacy percentage; further analysis is ongoing¹.

Read the caveats, because the company wrote them. The infant data highlight “the need for further evaluation of dose selection and vaccination scheduling”, and Valneva’s chief scientific officer, Hanneke Schuitemaker, speaks of results that underline “the need for further clinical evaluation and optimization”¹. A challenge study in American adults is not a field trial among toddlers in high-burden regions. The US Food and Drug Administration granted the candidate Fast Track designation in 2024; that speeds paperwork, not proof¹.

For you, the point is not the share price. It is that a disease that kills children mostly far from here has a candidate with a clean safety record, an immune response in the age group that matters, and one protection signal under controlled conditions, with the infant trial supported by Gates Foundation funding¹. That is how vaccines get made: slowly, in phases, with each gate written down in advance.