RT Journal Article SR Electronic T1 Key populations for early COVID-19 immunization: preliminary guidance for policy JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP E1620 OP E1632 DO 10.1503/cmaj.202353 VO 192 IS 48 A1 Shainoor J. Ismail A1 Linlu Zhao A1 Matthew C. Tunis A1 Shelley L. Deeks A1 Caroline Quach A1 , YR 2020 UL http://www.cmaj.ca/content/192/48/E1620.abstract