ahead of busy holiday travel and family gatherings, president joe biden acknowledged his administration s stprruggle to contain the largest spikes. there s a lot we don t know. i m sure you re going to ask me when is this going to end? how are we going to do this? reporter: president biden s simple answer to abc news david muir is we don t know for certain. uncertainty, as americans are eager to get tested, and thousands having to wait for long hours, and even longer waiting for those test results. more testing, including new federal sites and a half billion tests will be free to all americans. and more capacity to get shots in arms, including new mobile clinics. reporter: over the last couple days, president biden has touted his administration s efforts to provide americans with tools to protect themselves. on wednesday night, reacting to