As the U.S. ramps up rollout efforts to get more Americans vaccinated against the coronavirus, scientists in the UK are studying whether it's okay to mix COVID-19 vaccines. Participants in the new study will receive one AstraZeneca vaccine and one from Pfizer. If mixing is deemed safe, this could potentially make rollouts more flexible. Dr. Luiza Petre, Assistant Professor at Mt. Sinai School of Medicine, joined Wake Up With Cheddar to break down what we need to know.