Table 3.

Anti-spike protein IgG titres by vaccine schedule and age group in seronegative participants

	SARS-CoV-2 anti-spike protein IgG concentration, ELU/mL			Fold change
	Day 0 of third dose	Day 28 after third dose	Day 0 of fourth dose	Day 14 after fourth dose	Day 14 after fourth dose vs day 28 after third dose	Day 14 after fourth dose vs day 0 of fourth dose
Three doses of BNT162b2 plus BNT162B2
Age <70 years	5421 (4855–6054); 13	24 055 (22 180–26 088); 13	3895 (3486–4351); 13	35 116 (31 868–38 696); 12	1·37 (1·31–1·42); 12	8·45 (7·83–9·11); 12
Age ≥70 years	4047 (3551–4612); 18	29 314 (27 468–31 285); 18	3667 (3413–3940); 18	49 120 (45 756–52 730); 18	1·68 (1·60–1·75); 18	13·39 (12·68–14·15); 18
Three doses of BNT162b2 plus mRNA-1273
Age <70 years	4449 (4027–4916); 15	24 040 (22 444–25 748); 15	3203 (2971–3452); 15	46 053 (42 311–50 126); 15	1·92 (1·80–2·04); 15	14·38 (13·00–15·91); 15
Age ≥70 years	4812 (4255–5441); 18	34 253 (31 499–37 247); 18	6778 (5970–7695); 17	70 387 (66 103–74 947); 18	2·05 (1·97–2·15); 18	10·71 (9·79–11·72); 17
Two doses of ChAdOx1 nCoV-19 plus BNT162B2 plus BNT162B2
Age <70 years	1496 (1345–1663); 16	23 299 (21 376–25 395); 16	2630 (2415–2865); 16	34 582 (32 335–36 985); 16	1·48 (1·39–1·58); 16	13·15 (12·09–14·29); 16
Age ≥70 years	1154 (1067–1248); 19	18 409 (17 268–19 626); 19	2451 (2254–2665); 19	32 286 (29 965–34 787); 19	1·75 (1·65–1·86); 19	13·17 (12·09–14·35); 19
Two doses of ChAdOx1 nCoV-19 plus BNT162B2 plus mRNA-1273
Age <70 years	1416 (1240–1616); 14	21 607 (19 457–23 996); 14	2391 (2130–2683); 15	47 167 (43 536–51 102); 15	2·25 (2·04–2·48); 14	19·73 (17·59–22·13); 15
Age ≥70 years	1249 (1115–1400); 19	22 259 (20 225–24 499); 19	2722 (2454–3019); 19	56 318 (52 024–60 966); 19	2·53 (2·36–2·72); 19	20·69 (18·86–22·7); 19

Data are geometric mean (95% CI); number of participants contributing to analysis. ELU=ELISA laboratory units.