Figure 1.

In order to determine the feasibility of a vaccine trial, we estimated the required sample size and proportion of patients at high risk available to be included in a vaccine trial for a range of risk scores based on the final risk score developed in our model. For our example, we assumed a hospital with 20,000 annual patient index visits, and a vaccine efficacy of 50%, and we then plotted the necessary sample size and the estimated number at high risk for each risk score. For risk index scores up to 7, the number expected to be at high risk was greater than the estimated sample size.