Fig. 4. Further analyses of day 57 ID₅₀ level as a correlate of risk and as a correlate of protection.

(A) Covariate-adjusted cumulative incidence of COVID-19 by 100 days after day 57 by vaccinated baseline SARS-CoV-2–negative per-protocol subgroups defined by day 57 ID₅₀ level above a threshold, with reverse cumulative distribution function (CDF) of day 57 ID₅₀ level overlaid in green. The red dots are point estimates at 35 threshold values equally spaced over quantiles of the observed marker values, linearly interpolated by solid black lines. The gray shaded area is pointwise 95% CIs. The upper boundary of the green shaded area is the estimate of the reverse CDF of day 57 ID₅₀ level in baseline SARS-CoV-2–negative per-protocol vaccine recipients. The vertical red dashed line is the day 57 ID₅₀ threshold above which no post–day 57 COVID-19 end points occurred. (B) Covariate-adjusted cumulative incidence of COVID-19 by 100 days after day 57 by day 57 ID₅₀ level. The dotted black lines indicate bootstrap pointwise 95% CIs. The upper and lower horizontal gray lines are the overall cumulative incidence of COVID-19 from 7 to 100 days after day 57 in placebo and vaccine recipients, respectively. (C) Vaccine efficacy (VE) (solid black line) by day 57 ID₅₀ level, estimated using the method of Gilbert, Fong, and Carone (28). The dashed black lines indicate bootstrap pointwise 95% CIs. The horizontal gray line is the overall vaccine efficacy from 7 to 100 days after day 57, with the dotted gray lines indicating the 95% CIs [this number, 92.8%, differs from the 94.1% reported in (6), which was based on counting COVID-19 end points starting 14 days after day 29]. In (B) and (C), the green histograms are an estimate of the density of day 57 ID₅₀ level in baseline-negative per-protocol vaccine recipients. Baseline covariates are adjusted for baseline risk score, at risk status, and community of color status.