Vaxcyte Inc, a pioneering company at the forefront of vaccine development, has revealed the commencement of its phase 2 trial for VAX-31 in healthy infants. This marks an important milestone as the first participants have received their initial doses.
The aim of this study is to assess the safety, tolerability, and immune response elicited by VAX-31, a novel 31-valent pneumococcal conjugate vaccine (PCV) candidate created to thwart invasive pneumococcal disease (IPD).
Anticipated results from the primary immunization schedule, consisting of three doses, will be made public around mid-2026, followed by findings from the subsequent booster dose approximately nine months thereafter.
“Launching this phase 2 infant trial for VAX-31 is a key achievement in advancing our PCV initiatives, which also involve the fully recruited, ongoing VAX-24 infant trial,” stated Grant Pickering, co-founder and CEO of Vaxcyte. “Pneumococcal conjugate vaccines are essential in tackling the public health challenge posed by Streptococcus pneumoniae, especially given the rise in antimicrobial resistance. VAX-31, currently the most comprehensive PCV candidate in clinical studies, could expand coverage and offer protection against both existing and past serotypes. We eagerly await the safety, tolerability, and immunogenicity data from the primary series in mid-2026 and the booster phase thereafter.”
“Despite current vaccine successes, Streptococcus pneumoniae remains the top cause of preventable mortality among young children worldwide, with IPD continuously affecting children in their early years due to conditions like meningitis and bacteremia,” explained Jim Wassil, Vaxcyte’s executive vice president and COO. “The call from the health sector for a pneumococcal vaccine offering wider coverage remains strong. VAX-31 could potentially cover around 94% of IPD and 93% of acute otitis media in US children under five, offering significantly enhanced protection over current PCVs.”
The VAX-31 phase 2 infant trial follows a rigorous, randomized, double-blind design, comparing the candidate with Prevnar 20 (PCV20) in infants, initially focusing on dose-finding before moving on to broader evaluations with approximately 750 infants.
In alignment with guidelines from the Advisory Committee on Immunization Practices, the study involves a primary series with vaccinations at the ages of two, four, and six months, followed by a booster between 12 and 15 months.
Key outcomes will measure immune responses across VAX-31’s dose variations compared to PCV20 for both shared and unique serotypes, with evaluations post-third dose (PD3) and post-fourth dose (PD4).
Participants will be monitored for safety for half a year after the booster.
The trial is happening across roughly 50 locations throughout the United States.
Pneumococcal diseases (PD), caused by the bacterium Streptococcus pneumoniae, lead to serious conditions such as IPD and non-invasive diseases like pneumonia. It’s a major cause of bacterial meningitis and hospitalizations annually in the US. Due to resistance in some strains, there’s a pressing need for a vaccine with broader coverage, with Streptococcus pneumoniae listed as a major threat by health authorities.
In November 2024, Vaxcyte received the Breakthrough Therapy designation from the FDA for VAX-31 in adults as a preventive measure against IPD, speeding up its development for significant health conditions.