Impact of prior vaccination on clinical outcomes of patients with COVID-19

Figures & data

Table 1. Baseline characteristics of patients according to the vaccination status

	Vaccinated (n = 204)	Unvaccinated (n = 183)	p-value
Age, y	66.8 ± 14.3	47.8 ± 16.8	<0.001
Age category, y			<0.001
18–49	27 (13.2)	101 (55.2)
50–64	49 (24.0)	52 (28.4)
≥65	128 (62.7)	30 (16.4)
Sex			0.839
Male	103 (50.5)	90 (49.2)
Female	101 (49.5)	93 (50.8)
BMI, kg/m^2	25.2 ± 3.8	25.6 ± 5.0	0.357
PCR Gene Ct value	17.2 [13.8;21.2]	17.6 [14.7;21.4]	0.445
Co-morbidities
Hypertension	108 (52.9)	43 (23.5)	<0.001
Diabetes	46 (22.5)	26 (14.2)	0.037
Cardiovascular disease	35 (17.2)	26 (14.2)	0.486
Chronic lung disease	17 (8.3)	6 (3.3)	0.051
Chronic kidney disease	10 (4.9)	7 (3.8)	0.630
Chronic liver disease	3 (1.5)	8 (4.4)	0.125
Solid organ transplantation	3 (1.5)	2 (1.1)	>0.999
Rheumatic disorders	3 (1.5)	8 (4.4)	0.125
Cancer	16 (7.8)	11 (6.0)	0.552
Obesity (BMI>30)	31 (15.2)	31 (16.9)	0.679

Data are presented as number (%), median [interquartile range], or mean ± standard deviation.

Abbreviations: BMI, body mass index; PCR, polymerase chain reaction; Ct, cycle threshold.

Table 2. Types of vaccine product administered to the vaccinated group (n = 204)

	First dose	Second dose	Booster dose
ChAdOx1 nCoV-19	104 (51.0)	100 (49.0)	–
BNT162b2	94 (46.1)	98 (48.0)	11 (5.4)
mRNA-1273	1 (0.5)	1 (0.5)	2 (1.0)
Ad26.COV2.S	5 (2.5)		–

Data are presented as number (%).

Figure 1. Nationwide trends in COVID-19 cases, vaccination rates, and proportion of breakthrough infections among study patients (a) Cumulative number of confirmed COVID-19 cases in Republic of Korea during the study period. (b) Trends in vaccination rates in Republic of Korea during the study period. (c) Relative proportion of vaccinated and unvaccinated patients in the study patients. Abbreviations: COVID-19, coronavirus disease 2019

Figure 2. Kaplan-Meier curves of the respiratory failure-free survival by vaccination status. Kaplan-Meier survival curves of the probability of respiratory failure-free survival from hospital admission did not show a significant difference between the vaccinated and unvaccinated groups.

Table 3. COVID-19 presentation and clinical course according to the vaccination status

	Vaccinated (n = 204)	Unvaccinated (n = 183)	p-value
Asymptomatic infection, (%)	28 (13.7)	12 (6.6)	0.029
Hypoxia* at admission, (%)	20 (9.8)	32 (17.5)	0.036
Pneumonia, (%)	75 (36.8)	120 (65.6)	<0.001
Supplemental oxygen requirement	32 (15.7)	53 (29.0)	0.002
Respiratory failure	7 (3.4)	12 (6.6)	0.166
Transfer, (%)	7 (3.4)	11 (6.0)	0.239
Treatment, (%)
Remdesivir	34 (16.7)	51 (27.9)	0.010
Corticosteroid	45 (22.1)	62 (33.9)	0.012
Tocilizumab	3 (1.5)	6 (3.3)	0.317
Regdanvimab	130 (63.7)	85 (46.4)	0.001
Duration of oxygen supplementation, days	3.0 [2.0;4.8]	4.0 [2.0;6.0]	0.344
Time from symptom onset to discharge, days	10 [9;11]	11 [10;14]	<0.001

Data are presented as numbers (%) or medians [interquartile ranges].

*Hypoxia was defined as oxygen saturation <94% on room air at sea level.

Abbreviation: COVID-19, coronavirus disease 2019.

Table 4. Factors associated with COVID-19 pneumonia

	Unadjusted OR (95% CI)	p-value	Adjusted OR (95% CI)	p-value
Age	1.004 (0.993–1.015)	0.464
Male sex	1.269 (0.851–1.891)	0.242
BMI	1.001 (0.956–1.048)	0.975
PCR Ct value	0.996 (0.961–1.032)	0.839
Hypertension	0.703 (0.467–1.060)	0.092	1.005 (0.643–1.571)	0.982
Diabetes	1.482 (0.883–2.488)	0.136
Cardiovascular disease	1.118 (0.646–1.935)	0.692
Chronic lung disease	1.079 (0.464–2.508)	0.860
Chronic kidney disease	1.429 (0.532–3.834)	0.479
Chronic liver disease	1.750 (0.504–6.078)	0.378
Solid organ transplantation	1.484 (0.245–8.984)	0.667
Rheumatic disorders	0.553 (0.159–1.922)	0.352
Cancer	0.658 (0.297–1.456)	0.301
Obesity (BMI>30)	0.925 (0.536–1.597)	0.781
Prior vaccination	0.305 (0.201–0.463)	<0.001	0.305 (0.197–0.472)	<0.001

Abbreviations: COVID-19, coronavirus disease 2019; OR, odds ratio; CI, confidence interval; BMI, body mass index; PCR, polymerase chain reaction; Ct, cycle threshold.

Table 5. Factors associated with supplemental oxygen requirement

	Unadjusted OR (95% CI)	p-value	Adjusted OR (95% CI)	p-value
Age	1.020 (1.005–1.034)	0.007	1.046 (1.026–1.066)	<0.001
Male sex	1.102 (0.681–1.784)	0.693
BMI	1.033 (0.979–1.091)	0.238
PCR Ct value	1.005 (0.963–1.049)	0.826
Hypertension	1.195 (0.733–1.948)	0.476
Diabetes	1.760 (0.993–3.120)	0.053	1.581 (0.855–2.922)	0.144
Cardiovascular disease	1.189 (0.626–2.259)	0.596
Chronic lung disease	0.736 (0.243–2.223)	0.586
Chronic kidney disease	1.098 (0.349–3.458)	0.873
Chronic liver disease	1.345 (0.349–5.183)	0.667
Solid organ transplantation	0.887 (0.098–8.042)	0.915
Rheumatic disorders	0.348 (0.044–2.755)	0.317
Cancer	0.795 (0.292–2.167)	0.655
Obesity (BMI>30)	1.440 (0.773–2.683)	0.250
Prior vaccination	0.456 (0.278–0.748)	0.002	0.184 (0.098–0.345)	<0.001

Abbreviations: OR, odds ratio; CI, confidence interval; BMI, body mass index; PCR, polymerase chain reaction; Ct, cycle threshold.

Table 6. Factors associated with progression to respiratory failure

	Unadjusted OR (95% CI)	p-value	Adjusted OR (95% CI)	p-value
Age	1.031 (1.001–1.063)	0.043
Male sex	0.900 (0.357–2.266)	0.823
BMI	1.056 (0.963–1.159)	0.727
PCR Ct value	0.915 (0.830–1.009)	0.074	0.919 (0.830–1.018)	0.104
Hypertension	2.824 (1.086–7.344)	0.033
Diabetes	2.719 (1.031–7.172)	0.043
Cardiovascular disease	3.025 (1.074–8.518)	0.036	3.188 (1.121–9.064)	0.030
Chronic liver disease	0.503 (0.061–4.145)	0.523
Chronic kidney disease	4.741 (1.237–18.175)	0.023
Rheumatic disorders	1.989 (0.241–16.396)	0.523
Obesity (BMI>30)	0.320 (0.042–2.470)	0.275
Prior vaccination	0.506 (0.195–1.315)	0.162

Multivariable logistic regression model was performed using the backward LR method.

Abbreviations: OR, odds ratio; CI, confidence interval; BMI, body mass index; PCR, polymerase chain reaction; Ct, cycle threshold.

Data availability statement

Data are available upon reasonable request.