Table 1.

Summary of cohort and cross-sectional study results included in this systematic review.

Title	First author	Country	Number of participants	Findings
Adverse COVID-19 outcomes in immune deficiencies: Inequality exists between subclasses [16]	Karakoc Aydiner E.	Turkey	34	Overall, 67.6% of the patients required hospitalization and 23.5% required the ICU. The overall case fatality rate was 23.5%. The inpatient mortality rate was 34%. None of the admitted patients with predominantly antibody deficiencies died. Admitted patients with combined immunodeficiencies or immune dysregulation had mortality rates of 33% and 50% respectively.
CD19 + IgD + CD27- naïve B Cells as predictors of humoral response to COVID-19 mRNA vaccination in immunocompromised patients [17]	Schulz E.	Austria	25	After mRNA COVID-19 vaccination, patients with primary immunodeficiency had lower antibody production compared to healthy patients.
The clinical course and outcome of SARS-COVID 19 in patients with inborn errors of immunity, does it relate to the type of immune defects [18]	Sherkat R.	Iran	14	Not all patients with inborn errors of immunity are predisposed to severe COVID-19. Out of the 14 patients, 3 (21.4%) were hospitalized and 1 (7.1%) was admitted to the ICU.
Clinical outcome, incidence, and SARS-CoV-2 infection-fatality rates in Italian patients with inborn errors of immunity [11]	Milito C.	Italy	131	The cumulative incidence per 100,000 was 4.01 for patients with inborn errors of immunity and 5.22 for the general population. The infection fatality rate was 3.81% for patients with inborn errors of immunity and 3.28% for the general population. One third of the patients with inborn errors of immunity were positive for SARS-CoV-2 for over three weeks.
Clinical outcomes and features of COVID-19 in patients with primary immunodeficiencies in New York City [19]	Ho H.	United States	16	The median symptom duration was 29 days. Out of the 16 patients, 12 (75%) required hospitalization and 5 (31%) required the ICU. For oxygen supplementation, 5 (31%) required a standard nasal cannula and 5 (31%) required mechanical ventilation. Out of the 16 patients, 4 (25%) died.
Confirmed SARS-COV-2 Infection In A Cohort Of Children And Young Adults With Moderate Or Severe Primary Immunodeficiencies [13]	Deya-Martinez A.	Spain	65	The COVID-19 prevalence was 7.7% (5/65). Only one patient, with Jacobsen Syndrome and CVID-like phenotype, was symptomatic.
Coronavirus disease 2019 in patients with inborn errors of immunity: An international study [20]	Meyts I.	International	94	Out of the 94 patients with inborn errors of immunity and COVID-19, 59 (63%) required hospitalization, 13 (14%) required non-invasive ventilation, 15 (16%) required admission to the ICU, 15 (16%) required invasive ventilation, 3 (3%) required ECMO, and 9 (9.6%) patients died.
COVID-19 affecting hereditary angioedema patients with and without C1 inhibitor deficiency [21]	Grumach A.	Brazil	13	Out of the 13 patients with hereditary angioedema and COVID-19, 5 (38%) had a hereditary angioedema attack. One patient required hospitalization.
COVID-19 AND PRIMARY IMMUNODEFICIENCY: ONE-YEAR EXPERIENCE [22]	Al Yazidi L.	Oman	140	None of the children with primary immunodeficiencies were admitted to the hospital. A patient with XLA shed SARS-CoV-2 for 3 months.
COVID-19 in patients with primary and secondary immunodeficiency: The United Kingdom experience [23]	Shields A.	United Kingdom	67	Of the 67 patients with inborn errors of immunity, 34 (50.7%) required hospitalization, and 12 (17.9%) died. The inpatient mortality was 35.3% and the case fatality ratio was 28.5.
COVID-19 in Patients with Primary Immunodeficiency [24]	Esenboga S.	Turkey	26	Of the 26 patients, 8 (31%) were hospitalized, 2 (7.7%) were admitted to the ICU, and 2 (7.7%) died. The median recovery time was 8 days while one patient had a 60 day recovery time.
COVID-19 prevalence and outcomes in patients receiving biologic therapies at an infusion center in New York City [25]	Harada K.	United States	11	Of the 11 patients with primary immunodeficiency, 10 (91%) were hospitalized, 5 (45%) required a nasal canula, 4 (36%) required ventilation, 4 (36%) required the ICU, and 4 (36%) died.
Immunogenicity of Pfizer-BioNTech COVID-19 vaccine in patients with inborn errors of immunity [14]	Hagin D.	Israel	26	In response to the Pfizer-BioNTech COVID-19 vaccine, 18 out of 26 individuals with PI developed a specific antibody response and 19 had a S-peptide-specific T-cell response.
Impact of SARS-CoV-2 Pandemic on Patients with Primary Immunodeficiency [12]	Delavari S.	Iran	19	Compared to the general population, patients with primary immunodeficiencies had a 1.23 higher risk of COVID-19 infection. The general population had an incidence of 1:178 and patients with primary immunodeficiency had an incidence of 1:144.
Low morbidity in Danish patients with common variable immunodeficiency disorder infected with severe acute respiratory syndrome coronavirus 2 [26]	Drabe C.	Denmark	11	All 11 patients had CVID and recovered. Three (27%) of patients were admitted to the hospital and 1 (9%) patient required oxygen supplementation. The median symptom duration was 12 days.
Minor Clinical Impact of COVID-19 Pandemic on Patients With Primary Immunodeficiency in Israel [27]	Marcus N.	Israel	20	Out of 1679 primary immunodeficiency patients followed, 20 (1.2%) tested positive for COVID-19. None of the patients required hospitalization and symptom duration ranged from 1 to 14 days.
Risk factors for hospitalization, disease severity and mortality in children and adolescents with COVID-19: Results from a nationwide German registry [28]	Armann J.	Germany	169	Children with primary immunodeficiency had a 2.7-fold risk for ICU admission compared with children without primary immunodeficiency.
SARS-CoV-2 vaccine induced atypical immune responses in antibody defects: everybody does their best [15]	Salinas A.	Italy	75	Compared to healthy controls, patients with CVID had lower post BNT162b2 vaccination antibodies for Spike and RBD. Patients with XLA did not generate antibodies for Spike or RBD after vaccination. However, 5 out of 6 XLA patients developed Spike-specific T-cells.