Potential endpoint(s) to include to investigate objective • Proportion of pwCF with at least 1 seropositive result over the 2-year period • Seroprevalence according to age group • Seroprevalence according to geographical area • Seroprevalence according to CF disease genotype and severity. • Change in seroprevalence over time • Risk factors for infection in pwCF • Incidence of symptomatic COVID-19 over the 2 year study period and symptom severity • Proportion of seropositive pwCF with subsequent CF exacerbations compared to pwCF who are seronegative • Morbidity and mortality in pwCF with at least 1 seropositive result compared to pwCF who are seronegative • Levels and duration of anti-SARS-CoV-2 antibodies in pwCF following natural infection and vaccination SARS-CoV-2 • Analysis of these samples could include proteomic and genetic analysis and relating this to clinical outcome and antibody data collected as part of main study.

Potential endpoint(s) to include to investigate objective • Proportion of pwCF with at least 1 seropositive result over the 2-year period • Seroprevalence according to age group • Seroprevalence according to geographical area • Seroprevalence according to CF disease genotype and severity. • Change in seroprevalence over time • Risk factors for infection in pwCF • Incidence of symptomatic COVID-19 over the 2 year study period and symptom severity • Proportion of seropositive pwCF with subsequent CF exacerbations compared to pwCF who are seronegative • Morbidity and mortality in pwCF with at least 1 seropositive result compared to pwCF who are seronegative • Levels and duration of anti-SARS-CoV-2 antibodies in pwCF following natural infection and vaccination SARS-CoV-2 • Analysis of these samples could include proteomic and genetic analysis and relating this to clinical outcome and antibody data collected as part of main study.