>> let's get to kaylee hartung live with us from los angeles. we hear over and over again how important testing is, frustration about these potential negative results and also frustration from americans who are still telling us that they have found it difficult to even get a test? >> reporter: david, this analysis shows that it's not just important to get a test, it matters when you get tested. so if you have symptoms and get negative results it's recommended that you get another test. david? >> kaylee, thank you. we reported here on the president's hope for a vaccine by year's end. well, tonight there is promising news about the vaccine in trials at oxford and what the trials have revealed in monkeys. of course,hebvus question tonight --hat are the next steps? here's maggie rulli reporting from london. >> reporter: the study is small, but the results are promising. six rhesus monkeys were given a single dose of the vaccine. 14 days later, some of them developed protective antibodies against covid-19. 28 days later, all of them did.