A novel pneumococcal conjugate vaccine covering 25 serotypes, designated PCV25, has proven safe in infants and generated immune responses comparable to the current 20-valent vaccine, according to a phase II trial presented at the IDWeek annual meeting.
Immune Response and Safety in Infants
The trial included 401 healthy infants randomized to receive either PCV25 or PCV20 at 2, 4, and 6 months. A toddler dose was administered at 12 to 15 months. Immunogenicity was assessed one month after the fourth dose, showing similar responses between the two vaccines for their shared 20 serotypes.
Local reactions such as injection-site pain, redness, and swelling were mostly mild to moderate, with no significant differences between groups. Systemic events like fever and decreased appetite occurred at similar rates, and no grade 4 adverse events were reported.
Enhanced Coverage and Serotype 3 Improvements
It targets serotypes responsible for approximately 84% of invasive pneumococcal infections in U.S. children under five, offering about 25% more coverage than PCV20. The vaccine incorporates an enhanced formulation of serotype 3, which accounts for roughly 10% of such infections and has historically been difficult to immunize against effectively.
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Immune responses to serotype 3 improved significantly with it. The geometric mean concentration (GMC) of immunoglobulin G rose from 4 mcg/mL after the third dose to 13 mcg/mL after the fourth. In contrast, PCV20 responses to serotype 3 remained below 1 mcg/mL throughout the trial. For 17 of 20 serotypes, the percentage of infants reaching the 0.35 mcg/mL protection threshold was comparable between the two vaccines, with it showing higher coverage for serotype 3.
Future Development and Recommendations
Streptococcus pneumoniae causes conditions ranging from ear infections to pneumonia and meningitis. The American Academy of Pediatrics recommends four doses of PCV20 or PCV15 for infants starting at 2 months, while the CDC advises vaccination for all children under five and those at higher risk. Current vaccines cover between 15 and 23 serotypes.
PCV25 is currently undergoing phase III clinical trials. FDA approval submission is planned for 2029.