>> i still think we need to vaccinate another 80 million to 100 million people to get to the kind of levels of population immunity. >> reporter: and amplifying the threat to those who hesitate, the growing presence of the highly-transmissible delta variant. >> the delta variant is by far the most contagious variant we have seen in the entire pandemic. if you have been fully vaccinated, you remain protected. >> reporter: and tonight, the nation on the precipice of 600,000 americans killed by covid-19. michelle preissler lost her husband darryl last month. >> no, it's not over. and there are plenty of people with covid in the hospital very sick and dying still. >> a reminder that death toll is still mounting. trevor, this week, the cdc has scheduled a meeting about reports of heart inflammation in a small number of young vaccinated people. what are they saying? >> reporter: linsey, the cdc says there has been more than 200 of these cases confirmed in