The Levels of Anti-SARS-CoV-2 Spike Protein IgG Antibodies Before and After the Third Dose of Vaccination Against COVID-19

Figures & data

Table 1 Cohort Characteristics, Inclusion and Exclusion Criteria

Cohort Characteristics (n = 93)
Age:
● Mean (SD): 47.8 (9.5); median (Q1, Q3): 50.0 (45.0, 55.0); range: 21.0–61.0
Sex:
● Female: 70 (75.3%); Male: 23 (24.7%)
Profession:
● Medical: 44 (47.3%); non-medical: 49 (52.7%)
COVID-19 history:
● Negative: 62 (66.7%), positive: 31 (33.3%)
Chronic diseases:
● No data available: 2 (2.2%); no: 63 (67.7%); yes: 28 (30.1%)
The most common diseases: thyroid diseases (hypothyroidism, hyperthyroidism, Hashimoto’s disease [n = 13]), hypertension (n = 12), diabetes (n = 3)
Inclusion criteria:
● Age between 18 and 61 years (adult participants of pre-retirement age).  ● Two doses of vaccination against COVID-19.  ● No chronic severe diseases.  ● No history of COVID-19 in the last 6 months.  ● Participant’s declaration to take the third dose of the same vaccine. ● Donate whole blood (approx. 3 mL) four times within the prescribed period to test the level of antibodies IgG anti-SARS-CoV-2. ● Providing the required documentation (informed consent to participate in the study, medical data questionnaire).
Exclusion criteria:
● Age <18 and >61.  ● Unvaccinated people or one dose of vaccination.  ● Chronic and/or severe diseases in acute phase, untreated.  ● Positive history of COVID-19 in the last 6 months, participants who fell ill with COVID-19 during the project.  ● Missing 3 doses of vaccination.  ● Missing four blood measurements, untimely blood donation.  ● No required documentation.

Figure 1 Comparison of anti-SARS-CoV-2 IgG levels [IU/mL] among the examined participants.

Notes: The participants (n = 93) were tested at 4 time points (measurements) in relation to the third dose of COVID-19 vaccination (1st – approx. 2 weeks before vaccination, 2nd - approx. 3 months after vaccination, 3rd - approx. 5 months after vaccination, 4th - approx. 6 months after vaccination), dots – participants, red dots – outliers; error bars lines: bottom and top - quartiles Q1, Q3; middle - median of IgG levels; statistical significance (p < 0.05) was measured by Wilcoxon signed rank test; p-values for pairwise comparisons were all less than 0.0001, exception 2nd vs 3rd (p = 0.0415) and 2nd vs 4th (p = 0.0183).

Figure 2 Comparison of relative increase of anti-SARS-CoV-2 IgG levels.

Notes: The relative IgG was the ratio between value of IU/mL of IgG_2/IgG_1; the participants grouped according to four baseline IgG levels [IU/mL] ranges: <40 (2.12–39.3), 40≤100 (43.47–95.04), 100≤200 (102.28–191.66), >200 (211.3–1635); medians with interquartile range of relative IgG, the differences were measured by Mann Whitney exact test, two-tailed, unpaired (statistically significant p < 0.05).

Table 2 Comparison of the Medians (with Quartiles Q1, Q3) of the Anti-SARS-CoV-2 Spike IgG Antibodies Values [IU/mL] Among the Studied Participants (n = 93) Based on Specific Parameters (Age, Sex, COVID-19 History, Profession)

Measurements:		Median (Q1, Q3) Level of Anti-SARS-CoV-2 Spike IgG
		1st (IgG_1)	2nd (IgG_2)	3rd (IgG_3)	4th (IgG_4)
Age	Age≤49 (n=43)	72.60 (34.92, 194.15)	305.59 (213.88, 471.02)	292.20 (143.23, 528.91)	233.78 (121.15, 445.42)
	Age≥50 (n=50)	72.61 (21.42, 156.31)	405.40 (200.24, 665.08)	392.13 (171.52, 679.02)	380.99 (155.40, 696.22)
	p-value	0.3511	0.2477	0.3091	0.1982
Sex	Female (n=70)	71.54 (25.69, 181.15)	389.41 (230.48, 668.35)	382.86 (169.39, 679.02)	378.73 (161.57, 635.17)
	Male (n=23)	74.73 (23.76, 157.54)	293.04 (124.31, 399.00)	206.55 (142.56, 363.24)	187.18 (113.53, 473.54)
	p-value	0.6756	0.0348	0.0254	0.0873
COVID-19 history	Positive (n=31)	151.34 (60.36, 250.50)	295.10 (222.59, 467.08)	260.58 (162.58, 459.81)	209.32 (153.47, 390.91)
	Negative (n=62)	51.02 (17.09, 136.09)	389.41 (186.36, 665.08)	392.13 (149.02, 877.17)	393.00 (126.32, 759.36)
	p-value	0.0022	0.2988	0.1111	0.0862
Profession	Medical (n=44)	65.89 (33.64, 131.42)	389.41 (261.15, 664.93)	420.24 (264.76, 673.72)	380.99 (204.94, 655.65)
	Non-medical (n=49)	74.73 (21.68, 247.06)	296.88 (182.33, 521.77)	223.78 (141.92, 523.24)	192.31 (97.79, 513.17)
	p-value	0.3717	0.1704	0.0167	0.0160

Note: p-value was measured by Mann-Whitney test (Bold values indicated statistically significant p <0.05).

Table 3 Number (%) of Participants Grouped According to Particular Parameters (Age, Sex, COVID-19 History, Profession) Showing Specific Patterns of Trajectory of IgG Antibody Dynamics Between Consecutive Measurements

Trajectory of IgG Dynamics:		Number (%) of Participants									Overall p-value (F)
		DDD	ICC	ICD	IDC	IDD	IDI	IIC	IID	III
Age	Age≤49 (n=43)	5 (11.6)	0 (0.0)	3 (7.0)	3 (7.0)	19 (44.2)	1 (2.3)	1 (2.3)	7 (16.3)	4 (9.3)	0.10
	Age≥50 (n=50)	0 (0.0)	1 (2.0)	1 (2.0)	5 (10.0)	24 (48.0)	6 (12.0)	0 (0.0)	9 (18.0)	4 (8.0)
	p-value	Ns	Ns	Ns	Ns	Ns	Ns	Ns	Ns	Ns
Sex	Female (n=70)	3 (4.3)	0 (0.0)	4 (5.7)	8 (11.4)	32 (45.7)	5 (7.1)	1 (1.4)	12 (17.1)	5 (7.1)	0.36
	Male (n=23)	2 (8.7)	1 (4.3)	0 (0.0)	0 (0.0)	11 (47.8)	2 (8.7)	0 (0.0)	4 (17.4)	3 (13.0)
	p-value	Ns	Ns	Ns	Ns	Ns	Ns	Ns	Ns	Ns
COVID-19 history	Positive (n=31)	4 (12.9)	0 (0.0)	0 (0.0)	4 (12.9)	16 (51.6)	1 (3.2)	0 (0.0)	3 (9.7)	3 (9.7)	0.15
	Negative (n=62)	1 (1.6)	1 (1.6)	4 (6.5)	4 (6.5)	27 (43.5)	6 (9.7)	1 (1.6)	13 (21.0)	5 (8.1)
	p-value	Ns	Ns	Ns	Ns	Ns	Ns	Ns	Ns	Ns
Profession	Medical (n=44)	0 (0.0)	1 (2.3)	2 (4.5)	4 (9.1)	16 (36.4)	5 (11.4)	1 (2.3)	12 (27.3)	3 (6.8)	0.028
	Non-medical (n=49)	5 (10.2)	0 (0.0)	2 (4.1)	4 (8.2)	27 (55.1)	2 (4.1)	0 (0.0)	4 (8.2)	5 (10.2)
	p-value	0.0576 (F)	0.4731 (F)	1 (F)	1 (F)	0.0703 (χ^2)	0.2494 (F)	0.4731 (F)	0.0147 (χ^2)	0.7176 (F)

Note: p-value was measure by Fisher’s exact (F) or chi-square (χ²).

Abbreviations: D, decrease; I, increase; C, constant; ns, not significant.

Figure 3 Dynamics of anti-SARS-CoV-2 IgG of the participants according to age, sex, COVID-19 history and profession.

Notes: The dots represent the median levels of IgG at 4 measurements (1st – approx. 2 weeks before vaccination 3rd dose of vaccination, 2nd - approx. 3 months after vaccination, 3rd - approx. 5 months after vaccination, 4th - approx. 6 months after vaccination), the differences were measured by Wilcoxon signed rank test (statistically significant p < 0.05).