science. >> today israel's advisory group recommended a fourth covid vaccine for everyone. do you think that could happen in the united states and if so, how soon? >> i don't see that happening in the united states. one, we have not been as aggressive, as have some others have been, such as israel, around applying the science in new scenarios. we don't know definitively whether or not those higher antibody levels will necessarily reduce severe disease. meaning reducing hospitalization and fatality. because of that, we're going to focus on getting as many americans boosted and vaccinated. that doesn't mean we won't continue to watch with vigilance. and it doesn't mean those who are immuno compromised, that they won't be counselled or advised to get a fourth shot. >> so a world health