Pfizer (PFE) said Wednesday that its experimental 25-valent pneumococcal vaccine generated stronger immune responses than the company's currently approved PREVNAR 20 in a mid-stage infant study.

Preliminary phase 2 data showed antibody levels against serotype 3, a major remaining cause of pneumococcal disease in children, were significantly higher in infants receiving Pfizer's investigational vaccine candidate, 25vPnC, compared with Prevnar 20 after both the third and fourth doses, Pfizer said.

Pfizer said the vaccine candidate could potentially cover up to 90% of disease-causing pneumococcal serotypes in children under five years old.

The company said it has already started a pivotal pediatric phase 3 trial evaluating the vaccine in up to 2,400 healthy children.

Pfizer said it plans to move directly to a fifth-generation adult pneumococcal vaccine candidate covering 35 serotypes, which it expects to enter clinical development by the end of 2026.