Table 5.

Longitudinal Linear Mixed Modeling to Estimate Decay Kinetics of Log₁₀ Anti-Spike IgG Response to Antigenic Exposure

Covariates	Coefficient	P Value
Sampling time	−<0.01 (−<0.01 to −<0.01)	<.01
Vaccination after infectiona	0.13 (0.09 to 0.16)	<.01
Vaccine breakthrough infectiona	0.1 (0.06 to 0.14)	<.01
Vaccination alonea	0.15 (0.09 to 0.21)	<.01
Sampling time * Vaccine after infection	<0.01 (<0.01 to <0.01)	.03
Sampling time * Vaccine breakthrough infection	<0.01 (<0.01 to <0.01)	<.01
Sampling * Vaccination alone	−<0.01 (−<0.01 to −<0.01)	.02

Number of observations, 1160. Sampling time refers to last antigenic exposure, that is, time since final dose of vaccine or infection, whatever is latest. Model fit to all longitudinal data and including group, sampling time, and an interaction term of sampling time and group. The asterisk (*) is used to indicate interactions among the variables that it joins.

^aRef: SARS-CoV-2 infection alone.