Thousands of people received convalescent plasma as an experimental treatment for Covid. A new study shows that it works — but only when given within a few days of the onset of illness.
Author: Katherine J. Wu
Britain Opens Door to Mix-and-Match Vaccinations, Worrying Experts
If a second dose of one vaccine isn’t available, another may be substituted, according to the guidelines.
What People With Allergies Should Know About Covid Vaccines
Four people so far have had allergic reactions after getting the Pfizer-BioNTech vaccine. Experts say that shouldn’t deter most people from getting a jab.