What does Vaccine Efficacy Really Mean and How Might it Change?
Summary: The "efficacy" of a vaccine(VE) is a convenient number, but it's often provided without vital context that would ensure it is interpreted correctly. There are different kinds of efficacy that matter, and the numbers reported are often at peak levels following vaccination. It is in the commercial, professional, and political interest of drugmakers, the media, virologists, and policymakers to emphasize the highest number to demonstrate the power of the vaccines. The 3 primary outcomes that vaccination is intended to prevent are severe disease, infection, and transmission. The number for severe disease is likely to be highest, while the number for transmission is likely to be lowest. This is because different aspects of the immune response affect each. There are 3 main takeaways: VE is usually reported in terms of prevention of severe disease, VE can change against infection and severe disease independently, and SARS-CoV-2 is likely to escape from today...