Table 2.

Effect of a fourth SARS-CoV-2 vaccine dose and hybrid immunity on anti-RBD antibody concentrations, with adjustment for possible confounding factors

	Univariable analysis (unadjusted)	Multivariable analyses (adjusted)
	Median (BAU/mL)	Median (BAU/mL)	95% CI	p value
BNT162b2	6237	6647	5036–8258	1 (ref)
mRNA-1273	5993	5811	4342–7281	0·44
COVID-19	23 548	23513	21 226–25 801	<0·0001

Multivariable median regression model for the vaccine group versus the hybrid group with adjustments for possible confounding factors. All variables were prespecified. Covariates included in this model were age, sex, diagnosis, medication group, vaccine type, vaccine series, time from fourth vaccine dose or COVID-19 to sampling, time between third and fourth vaccine dose, and time from third vaccine dose to COVID-19. The dependent variable was anti-RBD antibody concentrations (BAU/mL). BAU=binding antibody units. RBD=receptor binding domain.