Table 2.

Vaccine Efficacy Against Symptomatic Covid-19 at Least 7 Days After the Second Dose (Day 28)

Population/Baseline Anti-Spike IgG Serostatus	No. of Cases	NVX-CoV2373*		Placebo		VE (95% CI)
		n/N (%)†	(95% CI)	n/N (%)†	(95% CI)
All Participants
Baseline seronegative (primary endpoint)	44	15/1357 (1.1)	(0.6, 1.8)	29/1327 (2.2)	(1.5, 3.1)	49.4%‡ (6.1, 72.8)
Baseline seropositive	19	6/500 (1.2)	(0.4, 2.6)	13/514 (2.5)	(1.4, 4.3)	52.6% (−23.8, 81.8)
Regardless of baseline serostatus	63	21/1857 (1.1)	(0.7, 1.7)	42/1841 (2.3)	(1.6, 3.1)	50.4% (16.6, 70.5)
HIV-Negative Participants
Baseline seronegative	38	11/1281 (0.90)	(0.43, 1.5)	27/1255 (2.2)	(1.4, 3.1)	60.1% (19.9, 80.1)
Baseline seropositive	19	6/467 (1.29)	(0.47, 2.8)	13/484 (2.7)	(1.4, 4.5)	52.2% (−24.8, 81.7)
Regardless of baseline serostatus	57	17/1748 (0.97)	(0.57, 1.6)	40/1739 (2.3)	(1.6, 3.1)	57.7% (25.7, 75.9)

Abbreviations: CI = confidence interval; Covid-19 = coronavirus 2 disease 2019; HIV = human immunodeficiency virus; N = number of participants; n = number of participants with NAAT-confirmed Covid-19; NAAT = nucleic acid amplification test; PP-EFF = per-protocol efficacy; VE = vaccine efficacy.

^*Includes 50 μg Matrix-M1.

^†Percentage of participants with Covid-19 calculated as n/N × 100.

^‡Primary endpoint.

The 95% CI for PCR-confirmed Covid-19 was calculated using the exact Clopper-Pearson method. Participants were counted once if the participant reported one or more PCR-confirmed illness episodes. Log-linear model of NAAT-confirmed Covid-19 infection incidence rate using Poisson regression with treatment group as fixed effects and robust error variance.²⁶ VE = 100 × (1 − Relative Risk). Data shown are for the PP-EFF analysis set (used for baseline seronegative analysis) or the PP-EFF-2 analysis set (used for baseline seropositive, or regardless of baseline serostatus, analysis).