Two Doctors from Earth: Which COVID-19 vaccine is safe and effective?

Currently, AstraZeneca Covid-19 vaccine has attracted the most attention globally, and as a result, the effectiveness of other Covid-19 vaccines is thrust into the limelight. It is known that China and U.S.A have approved 7 Covid-19 vaccines for emergency use. What are the differences between them? And which one is the most effective?

Speakers: 

- Dr. William Checkley (Associate Professor, Johns Hopkins University School of Medicine, a Critical Care Medicine Specialist at Johns Hopkins Hospital)

- Dr. Lina Tao (Vaccine Expert, Former Immunologist of Shanghai CDC)