Safety, immunogenicity, and reactogenicity of BNT162b2 and mRNA-1273 COVID-19 vaccines given as fourth-dose boosters following two doses of ChAdOx1 nCoV-19 or BNT162b2 and a third dose of BNT162b2 (COV-BOOST): a multicentre, blinded, phase 2, randomised trial

Safety, immunogenicity, and reactogenicity of BNT162b2 and mRNA-1273 COVID-19 vaccines given as fourth-dose boosters following two doses of ChAdOx1 nCoV-19 or BNT162b2 and a third dose of BNT162b2 (COV-BOOST): a multicentre, blinded, phase 2, randomised trial

SARS-CoV-2 anti-spike protein IgG concentration, ELU/mL Day 28 after the third dose 23 325 (20 030–27 162); 66 25 317 (20 996–30 528); 66 20 502 (16 473–25 517); 35 21 980 (16 476–29 324); 33 26 982 (22 056–33 008); 31 29 161 (23 093–36 823); 33 Day 0 of fourth dose 3049 (2550–3646); 66 3469 (2730–4407); 66 2532 (1974–3247); 35 2571 (1874–3527); 34 3761 (2959–4780); 31 4769 (3421–6648); 32 Day 14 after the fourth dose 37 460 (31 996–43 857); 65 54 936 (46 826–64 452); 67 33 316 (26 942–41 198); 35 52 080 (41 163–65 894); 34 42 949 (34 148–54 019); 30 58 043 (46 693–72 150); 33 Fold change (day 14 after fourth dose vs day 28 after third dose) 1·59 (1·41–1·78); 65 2·19 (1·90–2·52); 66 1·62 (1·35–1·95); 35 2·41 (1·90–3·05); 33 1·54 (1·35–1·76); 30 1·99 (1·71–2·31); 33 Fold change (day 14 after fourth dose vs day 0 of fourth dose) 12·19 (10·37–14·32); 65 15·90 (12·92–19·58); 66 13·16 (10·24–16·91); 35 20·26 (15·09–27·21); 34 11·14 (9·21–13·47); 30 12·30 (9·39–16·11); 32 Cellular response (wild-type), spot forming cells per 106 PBMCs

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Due to logistical reasons, only 50% of study sites collected cellular immunology samples (proximity to external laboratory) in the main COV-BOOST study; the cellular immunology samples after the fourth dose were collected in the immunology cohort.