Marc Lipsitch. (2021, July 20). At the risk of boiling down too much and certainly losing some detail, one way to summarize this wonderful thread is that when we think about vaccine effectiveness, we should think of 4 key variables: 1 which vaccine, 2 age of the person, 3 how long after vax, 4 vs what outcome. [Tweet]. @mlipsitch. https://twitter.com/mlipsitch/status/1417595538632060931