FDA Expands Pneumococcal Vaccine Indication for Children and Teens at High Risk

The U.S. Food and Drug Administration (FDA) has approved an expanded indication for Merck’s CAPVAXIVE (21-valent pneumococcal conjugate vaccine) to include children and teens aged 2-17 years who are at increased risk for pneumococcal disease, according to a press release from the manufacturer. The vaccine is now authorized for the prevention of invasive pneumococcal disease caused by 21 specific serotypes of *Streptococcus pneumoniae* in this high-risk population.

What Is CAPVAXIVE and How Does It Work?

CAPVAXIVE is a pneumococcal conjugate vaccine designed to stimulate the immune system to produce antibodies against 21 serotypes of *S. pneumoniae*, including 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15B, 15C, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F, and 35B. It was previously approved for adults aged 18 and older to prevent invasive disease and pneumonia. The new indication applies to children and teens with chronic medical conditions that increase their risk of pneumococcal infections, such as asthma, sickle cell disease, or immunocompromising conditions.

How Was the Approval Supported?

The FDA granted accelerated approval based on immune response data, specifically opsonophagocytic activity (OPA), a laboratory measure of antibody functionality. Merck cited results from the STRIDE-13 phase 3 trial, which enrolled 874 children and teens aged 2-17 with high-risk conditions. Participants had completed a primary pneumococcal vaccine series and were randomized to receive either CAPVAXIVE or the 23-valent pneumococcal polysaccharide vaccine (PPSV23).

Results showed CAPVAXIVE elicited significantly higher OPA geometric mean titers for nine serotypes unique to the vaccine compared to PPSV23. It was noninferior to PPSV23 for 12 shared serotypes and noninferior for serotype 15B in a post hoc analysis. The vaccine was administered as a single 0.5 mL intramuscular dose.

What Are the Safety Findings?

Both vaccines had similar safety profiles, with most adverse events resolving within three days. Serious adverse events occurred in 29 participants (CAPVAXIVE group) and 25 (PPSV23 group) over six months. Common side effects included injection site pain (67.7%), erythema (24.3%), fatigue (20.1%), swelling (18.8%), headache (17.1%), malaise (13.3%), and irritability (11.6%).

Why Does This Matter for Public Health?

This expansion broadens access to a vaccine that targets a wider range of pneumococcal serotypes, which may offer improved protection for children with chronic conditions. Pneumococcal disease remains a leading cause of vaccine-preventable illness, with invasive forms like meningitis and sepsis posing significant risks. The FDA’s decision aligns with recommendations from the Centers for Disease Control and Prevention (CDC), which emphasizes vaccination for high-risk groups.

What’s Next for CAPVAXIVE?

While the FDA’s accelerated approval hinges on continued monitoring, Merck noted that full approval could depend on confirmatory trials demonstrating clinical benefits. The agency’s decision underscores the importance of conjugate vaccines in eliciting stronger immune responses compared to polysaccharide vaccines like PPSV23, which are less effective in young children and immunocompromised individuals.