Table 4.

Patient characteristics and incidence of ITP exacerbation following SARS-CoV-2 vaccination

First vaccine doseSecond vaccine dose
nPlatelet count decrease ≥50%, n (%)Platelet count decrease >20% and nadir <30 × 109/L, n (%)Use of recue therapy, n (%)ITP exacerbation,* n (%)nPlatelet count decrease ≥50%, n (%)Platelet count decrease >20% and nadir <30 × 109/L, n (%)Use of rescue therapy, n (%)ITP exacerbation,* n (%)
All patients 111 16 (14.4) 10 (9) 7 (6.3) 19 (17.1) 70 14 (20) 10 (14.3) 9 (12.9) 14 (20) 
Splenectomy 25 11 (44) 8 (32) 6 (24) 12 (48) 19 7 (36.8) 4 (21) 4 (21) 7 (36.8) 
No splenectomy 86 5 (5.8) 2 (2.3) 1 (1.2) 7 (8.1) 51 7 (13.7) 6 (11.8) 5 (9.8) 7 (13.7) 
Relative Risk
[95% CI] 
    1.8
[1.3-2.8] 
    1.4
[1.02-2.2] 
0-4 prior medical therapies 54 2 (3.7) 2 (3.7) 3 (5.6) 3 (5.6) 43 7 (16.3) 6 (14) 6 (14) 7 (16.3) 
≥5 prior medical therapies 16 8 (50) 4 (25) 3 (18.8) 9 (56.3) 12 5 (41.7) 2 (16.7) 1 (8.3) 5 (41.7) 
Relative Risk
[95% CI] 
    2.2
[1.4-4.1] 
    1.4
[0.9-2.6] 
Prior rituximab use 39 9 (23.1) 4 (10.3) 3 (7.7) 10 (25.6) 26 9 (34.6) 5 (19.2) 5 (19.2) 9 (34.6) 
No prior rituximab use 56 4 (7.1) 4 (7.1) 4 (7.1) 6 (10.7) 34 5 (14.7) 5 (14.7) 4 (11.8) 5(14.7) 
Relative Risk
[95% CI] 
    1.2
[0.9-1.6] 
    1.3
[0.9-1.9] 
On current therapy for ITP 67 11 (16.4) 6 (9) 4 (6) 14 (20.9) 40 11 (27.5) 7 (17.5) 6 (15) 11 (27.5) 
No current therapy, prevaccine platelet count <150 × 109/L 30 4 (13.3) 3(10) 2 (6.7) 4 (13.3) 16 
No current therapy, prevaccine platelet count ≥150 × 109/L 14 1 (7.1) 1 (7.1) 1 (7.1) 1 (7.1) 1 (12.5) 1 (12.5) 1 (12.5) 1 (12.5) 
Any concurrent autoimmune disease 34 5 (14.7) 3 (8.8) 3 (8.8) 6 (17.6) 25 5 (20) 4 (10) 3 (12) 5 (20) 
No concurrent autoimmune disease 47 4 (8.5) 3 (6.4) 2 (4.3) 6 (12.8) 30 6 (20) 3 (16) 3 (10) 6 (20) 
Relative Risk
[95% CI] 
    1.06
[0.8-1.4] 
    1
[0.7-1.4] 
First vaccine doseSecond vaccine dose
nPlatelet count decrease ≥50%, n (%)Platelet count decrease >20% and nadir <30 × 109/L, n (%)Use of recue therapy, n (%)ITP exacerbation,* n (%)nPlatelet count decrease ≥50%, n (%)Platelet count decrease >20% and nadir <30 × 109/L, n (%)Use of rescue therapy, n (%)ITP exacerbation,* n (%)
All patients 111 16 (14.4) 10 (9) 7 (6.3) 19 (17.1) 70 14 (20) 10 (14.3) 9 (12.9) 14 (20) 
Splenectomy 25 11 (44) 8 (32) 6 (24) 12 (48) 19 7 (36.8) 4 (21) 4 (21) 7 (36.8) 
No splenectomy 86 5 (5.8) 2 (2.3) 1 (1.2) 7 (8.1) 51 7 (13.7) 6 (11.8) 5 (9.8) 7 (13.7) 
Relative Risk
[95% CI] 
    1.8
[1.3-2.8] 
    1.4
[1.02-2.2] 
0-4 prior medical therapies 54 2 (3.7) 2 (3.7) 3 (5.6) 3 (5.6) 43 7 (16.3) 6 (14) 6 (14) 7 (16.3) 
≥5 prior medical therapies 16 8 (50) 4 (25) 3 (18.8) 9 (56.3) 12 5 (41.7) 2 (16.7) 1 (8.3) 5 (41.7) 
Relative Risk
[95% CI] 
    2.2
[1.4-4.1] 
    1.4
[0.9-2.6] 
Prior rituximab use 39 9 (23.1) 4 (10.3) 3 (7.7) 10 (25.6) 26 9 (34.6) 5 (19.2) 5 (19.2) 9 (34.6) 
No prior rituximab use 56 4 (7.1) 4 (7.1) 4 (7.1) 6 (10.7) 34 5 (14.7) 5 (14.7) 4 (11.8) 5(14.7) 
Relative Risk
[95% CI] 
    1.2
[0.9-1.6] 
    1.3
[0.9-1.9] 
On current therapy for ITP 67 11 (16.4) 6 (9) 4 (6) 14 (20.9) 40 11 (27.5) 7 (17.5) 6 (15) 11 (27.5) 
No current therapy, prevaccine platelet count <150 × 109/L 30 4 (13.3) 3(10) 2 (6.7) 4 (13.3) 16 
No current therapy, prevaccine platelet count ≥150 × 109/L 14 1 (7.1) 1 (7.1) 1 (7.1) 1 (7.1) 1 (12.5) 1 (12.5) 1 (12.5) 1 (12.5) 
Any concurrent autoimmune disease 34 5 (14.7) 3 (8.8) 3 (8.8) 6 (17.6) 25 5 (20) 4 (10) 3 (12) 5 (20) 
No concurrent autoimmune disease 47 4 (8.5) 3 (6.4) 2 (4.3) 6 (12.8) 30 6 (20) 3 (16) 3 (10) 6 (20) 
Relative Risk
[95% CI] 
    1.06
[0.8-1.4] 
    1
[0.7-1.4] 
*

Defined as development of any 1 or more of the following: (1) ≥50% decline in platelet count from prevaccination baseline; (2) >20% decline from prevaccination baseline and platelet nadir <30 ×109/L; and/or (3) receipt of rescue therapy for ITP.

Prior rituximab use was specifically solicited in data collection as well as all prior treatment history.

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