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 | Â | Â | Â | Â |
 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 | Â | Â | Â | Â |
 Male | 309 | Reference | -- | -- |
 Female | 815 | 0.083 | -0.006–0.171 | 0.067 |
Type of profession | Â | Â | Â | Â |
 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 | Â | Â | Â | Â |
 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 | Â | Â | Â | Â |
 ≤ 50 days | 635 | Reference |  |  |
 > 50 days | 489 | -0.243 | -0.334 - -0.152 | < 0.001 |
Vaccination | Â | Â | Â | Â |
 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 |