Vaxcyte, Inc. announced an update regarding the ongoing progress of the Company's pneumococcal conjugate vaccine (PCV) franchise. These updates include the initiation of the Phase 2 portion of the ongoing VAX-31 adult Phase 1/2 study and encouraging input from ongoing discussions with the U.S. Food and Drug Administration (FDA) about the VAX-24 adult program to further inform the Company's chemistry, manufacturing and controls (CMC) licensure requirements. Vaxcyte's carrier-sparing PCV franchise candidates, including VAX-24, a 24-valent PCV proceeding to Phase 3, and VAX-31, the Company's next-generation 31-valent PCV, are being studied for the prevention of invasive pneumococcal disease (IPD).

Adult PCV Programs: VAX-31 Adult Program: The first participants were dosed in the Phase 2 portion of the ongoing Phase 1/2 study of VAX-31 in healthy adults. The initiation of the Phase 2 portion occurred after the independent Data Monitoring Committee reviewed the safety and tolerability data from the Phase 1 portion of the study and recommended that the study proceed as planned. This is a randomized, observer-blind, active-controlled, dose-finding study designed to evaluate the safety, tolerability and immunogenicity of VAX-31 at three dose levels compared to Prevnar 20® (PCV20) in approximately 1,000 healthy adults aged 50 and older.

Additional information about the study can be found at www.clinicaltrials.gov under the identifier NCT06151288. VAX-24 Adult Program: Following the Company?s successful End-of-Phase 2 meeting with the FDA regarding the VAX-24 adult Phase 3 clinical program, and as part of ongoing CMC-focused discussions, Vaxcyte received encouraging input from the FDA regarding the VAX-24 adult licensure requirements. The Company was granted these discussions under the VAX-24 adult Breakthrough Therapy designation and expects to seek additional CMC-focused input from the FDA as it prepares for and conducts its VAX-24 adult Phase 3 program.

The VAX-24 adult Phase 3 program will comprise several studies, including the pivotal, non-inferiority study which the Company expects to initiate in the second half of 2024. The Company expects to initiate the remaining Phase 3 studies, which are shorter in duration than the non-inferiority study, for the VAX-24 adult program in 2025 and 2026, and/or all the potential Phase 3 studies for the VAX-31 adult program during the same time period. Subject to the results of the Phase 3 studies, the Company would expect to submit a Biologics License Application (BLA) shortly following the completion of the last Phase 3 study.

VAX-24 Infant Program: The VAX-24 Phase 2 infant study continues to enroll participants in the second and final stage of the study. This is a randomized, observer-blind, dose-finding two-stage clinical study evaluating the safety, tolerability and immunogenicity of VAX-24 in healthy infants. The Stage 1 portion of the study evaluated the safety and tolerability of a single injection of VAX-24 at three dose levels and compared to VAXNEUVANCE?

(PCV15) in 48 infants. The Stage 2 portion, which commenced in July 2023, is evaluating the safety, tolerability and immunogenicity of VAX-24 for the prevention of IPD at the same three dose levels and compared to PCV20, currently the broadest-spectrum PCV recommended by the Advisory Committee on Immunization Practices, in approximately 750 infants. Anticipated Key Milestones: Based on the progress of its PCV franchise, Vaxcyte has updated anticipated timelines for all upcoming milestones, including: VAX-24 Adult Program: Initiation of the adult Phase 3 pivotal, non-inferiority study in the second half of 2024 with topline safety, tolerability and immunogenicity data in the second half of 2025.

VAX-24 Infant Program: Topline safety, tolerability and immunogenicity data from the primary three-dose immunization series of the ongoing infant Phase 2 study by the end of the first quarter of 2025, followed by topline data from the booster dose by the end of 2025. VAX-31 Adult Program: Topline safety, tolerability and immunogenicity data from the ongoing adult Phase 1/2 study in the third quarter of 2024.