it could be a combination of factors. so much to learn still, jim. >> cdc data does show that while hospitalizations among people are up, it's not near the increase you see in the vulnerable. vaccinated people who get coronavirus and suffer, they tend to be older, 80 years old on average. should that inform our understanding of who is most at risk right now as delta spreads? >> i think so. i think we also need to have perspective and realize that the people who are hospitalized, the people suffering severe outcomes are the unvaccinated. within that group we're going to find differences as to who has a predisposing condition, who is elderly, who is more vulnerable. when you look at teens, healthy teens -- this is data from cdc last friday.