What makes an mRNA vaccine so effective against severe COVID-19?

A new study from researchers at Washington University School of Medicine in St. Louis and St. Jude Children’s Research Hospital shines light on the quality of the immune response triggered by mRNA vaccines. The study shows that the Pfizer vaccine strongly and persistently activates a kind of helper immune cell that assists antibody-producing cells in creating large amounts of increasingly powerful antibodies, and also drives the development of some kinds of immune memory.