figure out how transmissible, how severe the disease this omicron will cause. having more of a buffer, more of a cushion is helpful. i think that's where that recommendation is coming from. >> omicron has become the dominant variant in south africa. less than two weeks since it was first detected. one doctor treating patients in south africa said cases have been mild for those infected with the omicron variant. does that give you less concern, less worry? >> i hope that remains true. there is -- a lot of epidemiologists talk about this pull and push of as a virus becomes more transmissible, it may becoming less lethal, causing less severe illness at the same time. somehow these may trade off. it's not a guarantee but that is a possibility here that is it becomes more transmissible, it becomes a less severe disease. so far we've heard most of the patients from south africa have also been young and they're likely to have more mild disease