Why Covid-19 Vaccines Take a While to Kick In – The New York Times

Reporting that a half-vaccinated person has Covid-19 is “really the equivalent of saying someone went outside in the middle of a rainstorm without an umbrella and got wet,” said Dr. Taison Bell, a critical care physician at the University of Virginia. Dr. Bell received his first dose of Pfizer’s vaccine on Dec. 15, and will be getting his second shot soon.

Data from Pfizer’s clinical trials suggests the vaccine might start safeguarding its recipients from disease around one or two weeks after the first injection. A second jab of mRNA, delivered three weeks after the first, helps immune cells commit the virus’s most prominent features to memory, clinching the protective process.