5:24
- ABC News
- July 20, 2021
What you need to know about breakthrough COVID-19 cases
ABC News contributor Dr. John Brownstein explains who is most at risk with the delta variant and what we know about existing vaccines’ ability to combat it.
5:24
ABC News contributor Dr. John Brownstein explains who is most at risk with the delta variant and what we know about existing vaccines’ ability to combat it.