https://www.annallergy.org/article/S1081-1206(22)01829-4/fulltext

By contrast, in the late time interval, IgG levels after the booster mRNA vaccine were approximately 3-fold higher (GM, 29.1 µg/mL [95% CI, 24.3-34.9]) compared with the primary series vaccination (GM, 9.5 µg/mL [95% CI, 8.1-11.1]) (P < .001) (Fig 2A). We then confirmed that there was a difference in trajectories between the booster and primary series by evaluating subjects who had paired early and late samples available. Linear regression indicated a slower IgG decay after the booster compared with the primary series vaccination, with respective slopes of −0.0024 (95% CI, −0.0037 to −0.0012) vs −0.0074 (95% CI, −0.0083 to −0.0065) (P < .001) (Fig 2B).