Merck's Capvaxive Shows Promise in Children, Expanding Beyond Senior Market

Merck's pneumococcal vaccine Capvaxive, originally designed for seniors, has demonstrated potential efficacy in children and adolescents, according to recent phase 3 trial results. This development could significantly expand the vaccine's market reach and impact on public health.

Trial Results Highlight Capvaxive's Efficacy in Younger Population

In a phase 3 study involving 882 participants aged 2 to 17 with chronic medical conditions, Capvaxive met key immunogenicity and safety endpoints. The trial, known as Stride-13, focused on children who had completed a primary pediatric pneumococcal vaccination regimen but remained at increased risk of respiratory disorders.

Capvaxive's performance was measured against Merck's established Pneumovax vaccine. In 12 shared serotypes, Capvaxive's immune response was comparable to Pneumovax 30 days post-vaccination. Notably, Capvaxive showed superior immune response in its nine unique serotypes.

Dr. Rotem Lapidot, chief of pediatric infectious diseases at Rambam Health Care Campus in Israel and a Stride-13 investigator, emphasized the importance of these findings: "Children and adolescents living with chronic medical conditions are at increased risk of pneumococcal disease and offering them additional protection is essential."

Expanding Coverage and Market Potential

Capvaxive's 21 serotypes account for 84% of pneumococcal disease in adults 50 and older, compared to 52% coverage by Pfizer's Prevnar 20, the current market leader. This broader coverage could prove beneficial for at-risk children and adolescents.

Paula Annunziato, head of Merck's infectious diseases and vaccines development, stated, "While Capvaxive was designed to specifically cover the serotypes that cause the majority of invasive pneumococcal disease cases in adults, findings from Stride-13 underscore its added potential to help protect children and adolescents who are at an increased risk."

Merck plans to share the trial data with global regulatory authorities, potentially paving the way for expanded use of Capvaxive. The vaccine has shown promising sales growth, increasing from $50 million in Q4 2024 to $129 million in Q2 2025.

As Capvaxive continues to demonstrate its versatility and efficacy across age groups, it may reshape the landscape of pneumococcal disease prevention, offering broader protection to vulnerable populations beyond its initial target market of seniors.