they started with those in that age group who were immunocompromised. is that the next step? israel has often been ahead of the u.s. on its vaccine program. is that what s next for us? i don t think we can say that s what s next in the sense that we re all looking carefully at how to best use these vaccines. they re remarkable tools but they re not perfect. if we end up finding ourselves in a position where we need to basically boost someone every six to seven months, that s going to be a challenge. we can t do that for the world. i think you re going to see a lot of discussion over the course of the next month or two as to just how should these vaccines be used. we went from a two dose mrna vaccine dose to a three-dose. now some places are looking at four dose, particularly for those who are immune compromised, and i think that the final answer is not in yet, how often we re going to use the vaccines. there are a lot of final answers that aren t in yet.