The purpose of this study is to learn about the safety, tolerability, and immunogenicity of an updated vaccine against COVID-19, called BNT162b2 (2025/2026 formulation).

This study is seeking participants 5 through 11 years of age who:

• have at least 1 underlying condition that puts them at high risk for severe outcomes from COVID-19,
• and are medically stable.

All participants in this study will receive 1 vaccine dose given in the muscle of their arm of a BNT162b2 (2025/2026 formulation) vaccine which targets the COVID-19 virus, specifically the strain selected for the 2025-2026 COVID-19 viral respiratory season.

Participants will take part in this study for about 6 months and will need to visit the clinical study site at least 2 times.

Key Inclusion Criteria:

• Children 5 through 11 years of age at their first appointment.
• Children with at least 1 underlying stable medical condition that increases their risk of severe COVID-19, as listed in the protocol.

Key Exclusion Criteria:

• Children who have had confirmed COVID-19 within the last 5 months (150 days).
• Children who have received a COVID-19 vaccine, either as part of a research study or an approved vaccine, within the last 5 months (150 days).
• Children who have received a 2025-2026 seasonal COVID-19 vaccination.
• Children with a history of myocarditis or pericarditis.
• Children with a previous or current diagnosis of Multisystem Inflammatory Syndrome in Children (MIS-C)
• Children with a medical condition wherein they would be considered for a second dose of COVID-19 vaccine to protect against risk of severe COVID-19 based on standard of care.

Refer to the study contact for further eligibility details.

This is an open-label study.