The purpose of the study is to evaluate the natural history of exocrine pancreatic function by assessing Fecal elastase-1 (FE-1) in infants with CF during their first year of life.

Key Inclusion Criteria:

• Participants with CF less than (<) 6 months of age at the index date
• Participants not eligible to receive commercial Kalydeco™ (based on local product labels) and are not receiving Kalydeco or any other cystic fibrosis transmembrane conductance regulator gene (CFTR) modulator

Key Exclusion Criteria:

• Participant whose mother took any CFTR modulator while pregnant with the participant, or who has any history of exposure to a CFTR modulator

Other protocol defined Inclusion/Exclusion criteria apply.

Infants with CF less than (<) 6 months of age at the index date who are not eligible for commercial Kalydeco™ (according to local product labels). The day of enrollment into this study will be referred to as the "index date".

Details on Vertex data sharing criteria and process for requesting access can be found at: https: https://www.vrtx.com/our-science/clinical-trials-data-sharing/