A) Difference in SARS-CoV-2 antibody seroconversion rate by week 4 after vaccination boost at baseline between 3rd mRNA SARS-CoV-2 (Biontech/Pfizer or Moderna) and vector SARS-CoV-2 vaccine (AstraZeneca). B) The efficacy of a 3rd mRNA boost vaccination in immunocompromised patients with inadequate humoral response (antibody titre <1500U/ml) to standard SARS-CoV-2 vaccination will be compared to low titre heathy controls by assessing the difference in antibody titre change before and after a second boost between the two groups.

A) Difference in SARS-CoV-2 antibody seroconversion rate by week 4 after vaccination boost at baseline between 3rd mRNA SARS-CoV-2 (Biontech/Pfizer or Moderna) and vector SARS-CoV-2 vaccine (AstraZeneca). B) The efficacy of a 3rd mRNA boost vaccination in immunocompromised patients with inadequate humoral response (antibody titre <1500U/ml) to standard SARS-CoV-2 vaccination will be compared to low titre heathy controls by assessing the difference in antibody titre change before and after a second boost between the two groups.

Difference in SARS-CoV-2 antibody seroconversion rate by week 4 after vaccination boost at baseline between 3rd mRNA SARS-CoV-2 (Biontech/Pfizer or Moderna) and vector SARS-CoV-2 vaccine (AstraZeneca).

Difference in SARS-CoV-2 antibody seroconversion rate by week 4 after vaccination boost at baseline between 3rd mRNA SARS-CoV-2 (Biontech/Pfizer or Moderna) and vector SARS-CoV-2 vaccine (AstraZeneca).