<qa>  What is the main purpose of this study?The main purpose of this study is to determine the dose of poly-ICLC that is safe and tolerable when it is combined with pembrolizumab in patients with colon cancer. This study will also evaluate how the combination of pembrolizumab and poly-ICLC activates the immune system in the patients blood and inside the tumor; how it affects the size and number of tumors in each patient; and how effective the combination is in patients with colon cancer that is unlikely to respond to pembrolizumab alone. 