Fig. 3: Administration of a vaccine booster significantly augments cross-nAb potency and breadth against sarbecovirus.

A Percentage of plasma samples with neutralizing effects against sarbecovirus-pseudotyped virus. The plasma samples were obtained from 25 COVID-19 convalescents before and after vaccination (upper panel) and 25 vaccinees before and after receiving a third booster dose (lower panel). A value of ID₅₀ > 30 was considered positive for neutralization. B Neutralization titers against sarbecovirus-pseudotyped virus for 25 COVID-19 convalescents before and after vaccination (upper panel) and for 25 vaccinees before and after receiving a third booster dose (lower panel). Paired t-tests were employed to examine the differences in neutralization titers pre- and post-vaccination for COVID-19 convalescents and pre- and post-booster vaccination for vaccinees. Significance levels are denoted as follows: *P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. A two-tailed test with P < 0.05 was considered statistically significant. ns, no significant. C Neutralization breadth for COVID-19 convalescents before and after vaccination (upper panel) and for vaccinees before and after receiving a third booster dose (lower panel) against sarbecoviruses. D Avidity indices of plasma sarbecovirus spike S1-specific IgG (upper panel) and S2-specific IgG (lower panel) for 25 COVID-19 convalescents before and after vaccination (left panel) and for 25 vaccinees before and after receiving a third booster dose (right panel). The convalescent plasma before vaccine administration was obtained at 248-387 days after illness onset (median=377; IQR = 371–382), while the convalescent plasma after vaccine administration was obtained at 15-201 days after third dose administration (median=118; IQR = 22-151). The plasma collected from vaccine recipients before receiving the booster dose was obtained at 271–307 days after a two-dose standard regimen (median=276; IQR = 275–278), while the plasma collected after receiving the booster dose was obtained at 14–92 days after a third booster dose (median=20; IQR = 18–24). Data are representative of technical triplicates. Data are presented as medians ± IQRs (25–75%), with error bars signifying the medians with IQRs. For C–D, the Mann–Whitney U test was employed to examine the differences pre- and post-vaccination for COVID-19 convalescents and pre- and post-booster vaccination for vaccinees. Significance levels are denoted as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. A two-tailed test with P < 0.05 was considered statistically significant. ns, no significant. nd, not detection. Conva, COVID-19 convalescents. Conva+Vac, COVID-19 convalescents after vaccination. Vac, individuals who received a two-dose vaccination. Vac+Booster, individuals who received a three-dose vaccination.