Table 3.

Multivariate linear regression model assessing factors associated with IgG antibody levels (logarithmic titres, BAU/mL) among those vaccinated three times (N = 1124^*)

Covariates	n (%)	Regression Coefficient	95% CI	p-value**
Age in years
16–29	182	Reference	--	--
30–39	308	-0.170	-0.287 – -0.052	< 0.01
40–49	275	-0.126	-0.247 – -0.004	< 0.05
50–59	275	-0.146	-0.272 – -0.020	< 0.05
60+	84	-0.174	-0.351–0.003	0.054
Gender
Male	309	Reference	--	--
Female	815	0.083	-0.006–0.171	0.067
Type of profession
Administration/Other facility management	263	Reference	--	--
Nurse	329	-0.134	-0.252–0.015	< 0.05
Physician	219	-0.254	-0.379 – -0.128	< 0.001
Other allied health professionals	313	-0.100	-0.210–0.010	0.076
Positive PCR test result for COVID-19
No	955	Reference
Yes, <=3 months	62	0.437	0.101–0.773	< 0.01
Yes, > 3 months	107	0.308	0.132–0.484	< 0.001
Time since last COVID-19 vaccine dose
≤ 50 days	635	Reference
> 50 days	489	-0.243	-0.334 - -0.152	< 0.001
Vaccination
2 doses BNT162b2 (3 weeks apart) + BNT162b2 booster	428	Reference	--	--
2 doses BNT162b2 (6 weeks apart) + BNT162b2 booster	124	0.035	-0.102–0.173	0.615
1 dose ChAdOx1-S, 1 dose BNT162b2 + BNT162b2 booster	366	-0.239	-0.350 – -0.129	< 0.001
2 doses ChAdOx1-S + BNT162b2 booster	155	-0.150	-0.280 – -0.024	< 0.05
Vaccine combinations with at least one dose mRNA-1273***	51	0.235	0.048–0.422	< 0.05

Abbreviation: CI: Confidence Interval

*Due to missing values in each of the covariates and exclusion of minor categories (i.e. non-binary gender, rare combinations of vaccines received) the number of participants reduces from 1201 participants with three vaccines received to 1124

**Bold represents p < 0.05

***These include: 1 dose ChAdOx1-S, 1 dose BNT162b2 + mRNA-1273 booster, 2 doses mRNA-1273 + BNT162b2 booster, 2 doses BNT162b2 + mRNA-1273 booster, 2 doses ChAdOx1-S + mRNA-1273 booster