KNTV NBC Nightly News With Lester Holt September 16, 2021 01:36:00
In january had a more than twofold increased risk for breakthrough infections versus those vaccinated in april. >> but the question is not about how the vaccines are doing today or last month. it's really how are they going to do this winter. >> reporter: the president of moderna telling nbc news their vaccine also shows waning protection against infection over time >> your data shows protection is dipping, but americans who are fully vaccinated are still protected from hospitalization. so why are boosters necessary? >> we do know as we get to a very large number of breakthrough cases, some of...