A Study to Learn Safety and Immune Response to Study Vaccine -RSVpreF in Adults at High Risk of Severe RSV Disease.

This is a Phase 3, multicenter, single-arm, open-label study that will assess the safety, tolerability, and immunogenicity of Pfizer's RSVpreF in adults 18 to 59 years of age considered to be at high risk of RSV disease due to certain chronic medical conditions in Japan.

Approximately 130 participants 18 to 59 years of age considered at high risk of RSV disease due to certain chronic medical conditions will be enrolled to receive RSVpreF.

The total duration of trial participation for each participant will be 2 months.

After screening and confirmation of eligibility, a prevaccination blood sample will be collected for immunogenicity assessments and a single dose of study intervention (RSVpreF) will be administered.

Participants will report daily reactogenicity data using an electronic device for 7-days or until resolution.

Participants will return approximately 1 month later for a follow-up blood draw for immunogenicity assessments and collection of safety information.

A telephone follow-up visit will be conducted approximately 2 months after vaccination to collect safety information.

Key Inclusion Criteria:

• Underlying health condition(s) that can put the participant at an increased risk of severe RSV/complications including chronic lung , heart, kidney, liver, nervous system, blood, or metabolic diseases

Key Exclusion Criteria:

• Received any kind of RSV vaccine before participating in this study
• Determined as not eligible by the investigator based on the participant's past and present health condition(s), medication(s) and treatment(s)

Please refer to the study contact for further eligibility details.