The following is a summary of “Safety and immunogenicity of a 4-component GMMA-based Shigella vaccine in healthy European adults: Stage 1 of a randomized, controlled phase I/II clinical trial,” published in the June 2024 issue of Infectious Disease by Leroux-Roels et al.

Researchers conducted a retrospective study of safety and immunogenicity data from Stage 1 of an ongoing two-staged, phase I/II randomized clinical trial with a 4-component Generalized Modules for Membrane Antigens-based vaccine against Shigella sonnei and S. flexneri 1b, 2a and 3a (altSonflex1-2-3, GSK).

They enrolled 102 Europeans aged 18 to 50 (N=102) and randomly assigned them (2:1) to receive either altSonflex1-2-3 or placebo with two injections, spaced 3 or 6 months apart. Safety and immune response were evaluated at specified intervals.

The results showed pain (altSonflex1-2-3: 97.1%; Placebo: 58.8%) and headache (32.4%; 23.5%) were standard after injections. The IgG antibodies peaked 14–28 days after the first injection and remained high at 3 or 6 months; the second injection restored initial immune levels. The highest response rates were against S. flexneri 2a (ELISA: post-injection 1: 91.0%; post-injection 2 [Day {D}113; D197]: 100%; 97.0%; SBA: post-injection 1: 94.4%; post-injection 2: 85.7%; 88.9%) followed by S. sonnei (ELISA: post-injection 1: 77.6%; post-injection 2: 84.6%; 78.8%; SBA: post-injection 1: 83.3%; post-injection 2: 71.4%; 88.9%). Responses against S. flexneri 1b and S. flexneri 3a were lower compared to S. sonnei and S. flexneri 2a.

Investigators concluded that altSonflex1-2-3 induced functional serotype-specific immune responses, allowing further clinical development in the target population. No safety signals or concerns were identified.

Source: academic.oup.com/jid/advance-article/doi/10.1093/infdis/jiae273/7690302