VAX-A1

June 2, 2026: Vaxcyte, Inc. (NASDAQ: PCVX) announced dosing of the first participant in a Phase 1 first-in-human trial of VAX-A1, an investigational prophylactic vaccine to prevent disease caused by Group A Streptococcus, in healthy adults ages 18–40. The randomized, double-blind, placebo-controlled, two-stage dose-escalation study (about 80 participants; ClinicalTrials.gov NCT07616934) will evaluate three dose levels vs placebo. Stage 1 enrolls ~12 participants (3:1 active:placebo across dose levels) with staged enrollment and internal safety review; after the Stage 1 Month 1 visit, an independent DSMB will review unblinded safety/tolerability data to allow progression to Stage 2 (~68 participants; 1:1:1:1 to three dose levels or placebo). Participants receive two doses ~two months apart and are followed for safety for ~6 months after the second dose.

Primary endpoints are safety/tolerability (including solicited/unsolicited AEs, SAEs, AESIs); secondary endpoints assess antigen-specific immune responses (IgG) to ScpA, SLO, SpyAD, and modified Group A carbohydrate (GACPR). The study is being conducted at a site in Australia. Vaxcyte expects to report topline Phase 1 data in 2H 2027.