TABLE 1.

Demographics and clinical characteristics of study participants who provided an antibody titer 1 month after vaccine 2, stratified by humoral response

n (%)	Positive response after vaccine 2 (n = 33)^a	Negative response after vaccine 2 (n = 12)^a	p-value^b
Demographics
Age group, years			1.0
12–15	28 (84.9)	11 (91.7)
16+	5 (15.2)	1 (8.3)
Sex, male	14 (42.4)	5 (41.7)	1.0
Race, white^c	22 (71)	9 (90)	.4
Hispanic or Latino, yes^d	2 (6.3)	0 (0)	1.0
Transplant characteristics
Organ			.068
Liver	17 (51.5)	2 (16.7)
Kidney	8 (24.2)	5 (41.7)
Heart	8 (24.2)	4 (33.3)
Liver-kidney	0 (0)	1 (8.3)
Time since transplant, years			.024
<3	2 (6.1)	5 (41.7)
3–11	18 (54.6)	4 (33.3)
≥12	13 (39.4)	3 (25)
<3 vs ≥3 Years since transplant			.010
Immunosuppression regimen
Number of agents^e			.013
0	1 (3.1)	1 (10)
1	15 (46.9)	0 (0)
2	10 (31.3)	4 (40)
3+	6 (18.8)	5 (50)
Single vs multiple agents (2+)^e			.031
Agents used^f
Tacrolimus^g	29 (87.9)	10 (90.9)	1.0
Anti-metabolite^h	14 (42.4)	10 (83.3)	.020
Sirolimusⁱ	6 (18.8)	1 (10)	1.0
Corticosteroids	5 (15.2)	5 (41.7)	.10
Cyclosporine	3 (9.1)	0 (0)	.6
Treated for rejection in past 6 months^j, ^k	1 (3.3)	1 (10)	.4

^{^a}

Table includes any patient in the study who had an antibody result available one month after their second vaccine, regardless of whether the patient was positive or negative after their first vaccine. Table does not include patients who reported a prior history of COVID, history of a pre-vaccination positive SARS-CoV-2 antibody test, or positive baseline serology in our study.

^{^b}

All univariate statistical comparisons were performed using the Fisher’s exact test.

^{^c}

Four missing (2 positive, 2 negative).

^{^d}

Three missing (1 positive, 2 negative).

^{^e}

Three patients excluded because of incomplete data.

^{^f}

Includes reported immunosuppression agents used at start of the study or at time of vaccine 1. Immunosuppression was not mutually exclusive, as some patients were on multiple agents. 0 patients were on everolimus or belatacept for their baseline immunosuppresion regimen prior to this study. 0 patients reported being on medications for other immune conditions including adalimumab, anakinra, baricitinib, belimumab, budesonide, certolizumab, cyclophosphamide, etanercept, hydroxychloroquine, infliximab, leflunomide, methotrexate, natalizumab, ocrelizumab, rituximab, sulfasalazine, tocilizumab, tofacitinib, and ustekinumab.

^{^g}

One missing (negative).

^{^h}

Includes myophenolate mofetil, mycophenolic acid, or azathioprine.

^ⁱ

Three missing (1 positive, 2 negative).

^{^j}

Five missing (3 positive, 2 negative).

^{^k}

No patients received rituximab, IVIG, plasma exchange, or thymoglobulin in the 6 months prior to this study.