“The 90% refers to preventing symptomatic disease (that is, fever, cough). But we don’t know yet how well this vaccine prevents severe symptoms that lead to hospitalizations, ICU admissions, and death. Knowing that will be key.”

—Robert Wachter, MD, Professor & Chair, Dept of Medicine, UCSF, We Hoped a Covid Vaccine Would Be Effective. But 90% Efficacy Is a True Game-Changer.