Coronavirus disease 2019 (COVID-19) which is caused by the virus SARS-CoV-2 has resultedin an ongoing global pandemic. It is unclear whether the relatively low number ofreported cases of COVID-19 in people with CF (pwCF) is due to enhanced infectionprevention practices or whether pwCF have protective genetic/immune factors. This studyaims to prospectively assess the proportion of pwCF, including both adults and childrenwith CF who have evidence of SARS-CoV-2 antibodies over a two-year period. This studywill also examine whether pwCF who have antibodies for SARS-CoV-2 have a differentclinical presentation and what impact this has on their CF disease. The proposed studywill recruit pwCF from paediatric and adult CF centres in Europe. Serological testing todetect antibodies will be performed on blood samples taken at month 0, 6, 12, 18 and 24with additional time-points if bloodwork is available via normal clinical care. Clinicaldata on, lung function, CF-related medical history, pulmonary exacerbations, antibioticuse, and microbiology and vaccination receipt, will be collected during routine clinicalassessments. Associations will be examined between socio-demographic and clinicalvariables and serologic testing. The effects of SARS-CoV-2 infection on clinical outcomesand analyse end-points will be examined to explore any age-related or gender-baseddifferences, as well as subgroup analysis of outcomes in lung-transplant recipients andpwCF receiving CFTR modulator therapies. As pwCF receive COVID-19 vaccination acomparison of the development and progression of anti-SARS-CoV-2 antibodies in pwCFfollowing natural infection and vaccination SARS-CoV-2 over time will be performed