but it is not just cases that are rising. so is the number of people needing hospital care. even as more healthcare workers get sent home sick. teachers, as well. with millions of kids going back to school today, mostly in person but in several large school districts they have gone back to remote learn for the time being. against that backdrop, today the fda signed off on booster doses of pfizer's vaccine for 12 to 15-year-olds and shortened the waiting period between second and third doses to five months from six. meantime, testing remains hard to get. questions about how dangerous low omicron is in general, and specifically to kids remain unanswered. early developments on that front as well. guidelines on isolation. the effectiveness of home testing kits, mask wearing remain confusing or controversial and sometimes even contradictory. feels like a lot to process because it is a lot to process so tonight we want to devote plenty of time to answering the questions most of us still have. our randi kaye starts us off with a quick rundown. >> reporter: what are we supposed to think about rapid tests?