This supplementary appendix provides additional information and methods for the study "Waning immune humoral response to BNT162b2 Covid-19 vaccine over 6 months" by Levin et al. in the *New England Journal of Medicine*. It includes detailed supplementary materials such as: 1. **Supplementary Methods**: - **PCR Testing**: Describes the testing protocols for hospital personnel, including various platforms used for qRT-PCR. - **Inclusion Criteria for Neutralizing Antibody Subgroup**: Lists specific medical conditions that qualify individuals for the neutralizing antibody subgroup. - **Antibody Detection**: Details the methods for SARS-CoV-2 IgG and neutralizing antibody assays, including the use of commercial tests and pseudovirus neutralization assays. - **IgG Linear Mixed Model**: Explains the statistical model used to analyze IgG levels over time, including random and fixed effects. - **Neutralizing Antibody Linear Mixed Model**: Similar to the IgG model, but focuses on neutralizing antibody levels and includes a change point at 70 days post-vaccination. 2. **Supplementary Results**: - **IgG Linear Mixed Model**: Provides the output of the basic and comorbidity models, including random and fixed effects. - **Neutralizing Antibody Linear Mixed Model**: Similar to the IgG model, with additional details on the change point at 70 days. 3. **Supplementary Tables**: - **Baseline Characteristics**: Summarizes the demographic and comorbidity characteristics of the study population. - **Demographic and Comorbidity Distribution**: Breaks down the distribution of demographic and comorbidity factors according to test periods. - **Expected and Observed GMTs**: Shows the geometric mean titers (GMTs) of IgG and neutralizing antibodies in each period. - **Monthly Trajectories**: Provides visual representations of antibody trajectories over time for participants with repeated tests. - **Monthly Correlation**: Displays the correlation between IgG and neutralizing antibodies over time. 4. **Supplementary Figures**: - **Monthly Trajectories**: Graphs the monthly changes in IgG and neutralizing antibody levels for participants with multiple tests. - **Monthly Correlation**: illustrates the association between IgG and neutralizing antibodies over time. 5. **Supplementary References**: Cites relevant studies and articles used in the supplementary materials.This supplementary appendix provides additional information and methods for the study "Waning immune humoral response to BNT162b2 Covid-19 vaccine over 6 months" by Levin et al. in the *New England Journal of Medicine*. It includes detailed supplementary materials such as: 1. **Supplementary Methods**: - **PCR Testing**: Describes the testing protocols for hospital personnel, including various platforms used for qRT-PCR. - **Inclusion Criteria for Neutralizing Antibody Subgroup**: Lists specific medical conditions that qualify individuals for the neutralizing antibody subgroup. - **Antibody Detection**: Details the methods for SARS-CoV-2 IgG and neutralizing antibody assays, including the use of commercial tests and pseudovirus neutralization assays. - **IgG Linear Mixed Model**: Explains the statistical model used to analyze IgG levels over time, including random and fixed effects. - **Neutralizing Antibody Linear Mixed Model**: Similar to the IgG model, but focuses on neutralizing antibody levels and includes a change point at 70 days post-vaccination. 2. **Supplementary Results**: - **IgG Linear Mixed Model**: Provides the output of the basic and comorbidity models, including random and fixed effects. - **Neutralizing Antibody Linear Mixed Model**: Similar to the IgG model, with additional details on the change point at 70 days. 3. **Supplementary Tables**: - **Baseline Characteristics**: Summarizes the demographic and comorbidity characteristics of the study population. - **Demographic and Comorbidity Distribution**: Breaks down the distribution of demographic and comorbidity factors according to test periods. - **Expected and Observed GMTs**: Shows the geometric mean titers (GMTs) of IgG and neutralizing antibodies in each period. - **Monthly Trajectories**: Provides visual representations of antibody trajectories over time for participants with repeated tests. - **Monthly Correlation**: Displays the correlation between IgG and neutralizing antibodies over time. 4. **Supplementary Figures**: - **Monthly Trajectories**: Graphs the monthly changes in IgG and neutralizing antibody levels for participants with multiple tests. - **Monthly Correlation**: illustrates the association between IgG and neutralizing antibodies over time. 5. **Supplementary References**: Cites relevant studies and articles used in the supplementary materials.