07:25 AM EDT, 09/11/2025 (MT Newswires) -- Merck ( MRK ) said Thursday that a phase 3 trial of its experimental vaccine, Capvaxive, for children and adolescents aged two to under 18 with chronic medical conditions that increase their risk of pneumococcal disease, showed strong immune responses to all 21 targeted serotypes.

The drugmaker said its vaccine was non-inferior to PPSV23 for the 12 shared serotypes and superior for the nine unique serotypes.

The proportion of participants with adverse events, including systemic and serious vaccine-related events, was generally similar between the two groups, the company said.

It added that the data mark the final results of the study, which is part of its broader Phase 3 program, and will be submitted to global regulators.