| E.1 Medical condition or disease under investigation | 
| E.1.1 | Medical condition(s) being investigated | 
| Patients with immune deficiency without proper response to previous SARS-CoV-2 vaccine doses. |  | 
| E.1.1.1 | Medical condition in easily understood language | 
| Vaccination for protection against COVID-19 |  | 
| E.1.1.2 | Therapeutic area | Diseases [C] - Immune System Diseases [C20] | 
| MedDRA Classification | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.0 |  
| E.1.2 | Level | HLGT |  
| E.1.2 | Classification code | 10003816 |  
| E.1.2 | Term | Autoimmune disorders |  
| E.1.2 | System Organ Class | 10021428 - Immune system disorders |  | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.0 |  
| E.1.2 | Level | PT |  
| E.1.2 | Classification code | 10074555 |  
| E.1.2 | Term | Transplantation complication |  
| E.1.2 | System Organ Class | 10022117 - Injury, poisoning and procedural complications |  | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.0 |  
| E.1.2 | Level | HLT |  
| E.1.2 | Classification code | 10003921 |  
| E.1.2 | Term | B-cell unclassifiable lymphomas |  
| E.1.2 | System Organ Class | 100000004851 |  | 
| E.1.3 | Condition being studied is a rare disease | No | 
| E.2 Objective of the trial | 
| E.2.1 | Main objective of the trial | 
| To investigate the immune response of a third SARS-CoV-2 mRNA vaccine dose in immunosuppressed patients with no or suboptimal vaccine response after the second dose. To investigate adverse events potentially linked to the third/fourth vaccine dose.
 |  | 
| E.2.2 | Secondary objectives of the trial | 
| To investigate the immune response of a fourth SARS-CoV-2 mRNA vaccine dose in solid organ transplant recipients with no or suboptimal vaccine response after the third dose and to investigate the sustained immune response long-term. |  | 
| E.2.3 | Trial contains a sub-study | No | 
| E.3 | Principal inclusion criteria | 
| •	Patients already included in one of the following ongoing vaccine observational subprotocols: •	SARS-CoV-2 cellular and humoral immune response following vaccination of kidney transplant recipients and healthy controls
 •	SARS-CoV-2 serological vaccine response in patients at Oslo University Hospital
 •	Vaccine responses in MS: Nevrovax.
 •	A Norwegian study of vaccine response to COVID-19 vaccines in patients using immunosuppressive medication within rheumatology and gastroenterology – The Nor-vaC study
 •	Immunological response to Covid-19 vaccination in Lymphoma patients treated with Rituximab and in Bone marrow Transplanted patients.
 •	Patients with an interval between the first and second vaccine dose according to drug label; 3 weeks for Comirnaty and 4 weeks for SpikeVax.
 •	Patients with no or impaired humoral immune response more than 3 weeks after two doses of SARS-CoV-2 mRNA vaccine (SARS-CoV-2 SPIKE IgG ≤100 AU).
 •	Available for vaccination at a few centralized centers (OUS, AHUS, Diakonhjemmet Hospital, HUS).
 •	Not participating in therapeutical intervention studies.
 •	Adult patients (≥18 years).
 •	For fourth dose: Solid organ transplant recipients with no or impaired humoral immune response 4 weeks after three doses of SARS-CoV-2 mRNA vaccine (SARS-CoV-2 SPIKE IgG ≤100 AU).
 
 |  | 
| E.4 | Principal exclusion criteria | 
| •	The second/third vaccine dose less than 4 weeks prior to vaccination with the third/fourth dose. •	Pregnant patients or women of childbearing potential (WOCBP) not on highly effective contraception (not acceptable methods: progesterone-only oral hormonal contraception, male/female condom without spermicide or cap, diaphragm or sponge with spermicide).
 •	Solid organ transplant recipients transplanted less than 6 months before the third dose vaccination.
 •	Serious side effect of previous SARS-CoV-2 vaccination.
 •	Allergic to any vaccine excipients.
 •	Acute febrile illness or acute infection.
 •	Received any vaccination against other infectious diseases within the last four weeks prior to the third dose.
 •	Have experienced breakthrough SARS-CoV-2 infection during or following primary vaccination.
 •	Participation in other vaccine studies.
 
 
 |  | 
| E.5 End points | 
| E.5.1 | Primary end point(s) | 
| Efficacy: SARS-CoV-2 SPIKE/RBD IgG antibody levels 4 weeks after administration of the third vaccine dose. Safety: Hospital admissions or deaths due to vaccine adverse events 6 weeks after the third/fourth dose.
 
 |  | 
| E.5.1.1 | Timepoint(s) of evaluation of this end point | 
| 4 weeks after administration of the third vaccine dose for the efficacy end point. 6 weeks after administration of the third vaccine dose for the safety end point.
 |  | 
| E.5.2 | Secondary end point(s) | 
| SARS-CoV-2 SPIKE/RBD IgG antibody levels 4 weeks after administration of the fourth vaccine dose. Humoral immune response at 3- and 6-months and sustained response up to 1 year after the third/fourth dose. Cellular immune responses at 4 weeks, 3- and 6 months and sustained response up to 1 year after the third/fourth dose in a subset of patients. Length of sustained humoral immune response following three versus two doses or four versus two doses. 
 |  | 
| E.5.2.1 | Timepoint(s) of evaluation of this end point | 
| Up to 1 years after the third/fourth vaccine doses. |  | 
| E.6 and E.7 Scope of the trial | 
| E.6 | Scope of the trial | 
| E.6.1 | Diagnosis | No | 
| E.6.2 | Prophylaxis | Yes | 
| E.6.3 | Therapy | No | 
| E.6.4 | Safety | Yes | 
| E.6.5 | Efficacy | Yes | 
| E.6.6 | Pharmacokinetic | No | 
| E.6.7 | Pharmacodynamic | No | 
| E.6.8 | Bioequivalence | No | 
| E.6.9 | Dose response | No | 
| E.6.10 | Pharmacogenetic | No | 
| E.6.11 | Pharmacogenomic | No | 
| E.6.12 | Pharmacoeconomic | No | 
| E.6.13 | Others | No | 
| E.7 | Trial type and phase | 
| E.7.1 | Human pharmacology (Phase I) | No | 
| E.7.1.1 | First administration to humans | No | 
| E.7.1.2 | Bioequivalence study | No | 
| E.7.1.3 | Other | No | 
| E.7.1.3.1 | Other trial type description |  | 
| E.7.2 | Therapeutic exploratory (Phase II) | No | 
| E.7.3 | Therapeutic confirmatory (Phase III) | No | 
| E.7.4 | Therapeutic use (Phase IV) | Yes | 
| E.8 Design of the trial | 
| E.8.1 | Controlled | Yes | 
| E.8.1.1 | Randomised | No | 
| E.8.1.2 | Open | Yes | 
| E.8.1.3 | Single blind | No | 
| E.8.1.4 | Double blind | No | 
| E.8.1.5 | Parallel group | Yes | 
| E.8.1.6 | Cross over | No | 
| E.8.1.7 | Other | No | 
| E.8.2 | Comparator of controlled trial | 
| E.8.2.1 | Other medicinal product(s) | No | 
| E.8.2.2 | Placebo | No | 
| E.8.2.3 | Other | Yes | 
| E.8.2.3.1 | Comparator description | 
| Patients vaccinated with only two mRNA doses |  | 
| E.8.2.4 | Number of treatment arms in the trial | 1 | 
| E.8.3 | The trial involves single site in the Member State concerned | No | 
| E.8.4 | The trial involves multiple sites in the Member State concerned | Yes | 
| E.8.4.1 | Number of sites anticipated in Member State concerned | 3 | 
| E.8.5 | The trial involves multiple Member States | No | 
| E.8.6 Trial involving sites outside the EEA | 
| E.8.6.1 | Trial being conducted both within and outside the EEA | No | 
| E.8.6.2 | Trial being conducted completely outside of the EEA | No | 
| E.8.7 | Trial has a data monitoring committee | No | 
| E.8.8 | Definition of the end of the trial and justification where it is not the last
                        visit of the last subject undergoing the trial |  | 
| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.1 | In the Member State concerned years | 1 | 
| E.8.9.1 | In the Member State concerned months | 6 | 
| E.8.9.1 | In the Member State concerned days | 0 |