RT Journal Article SR Electronic T1 Booster uptake stalling as experts debate fourth COVID shots JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP E532 OP E533 DO 10.1503/cmaj.1095993 VO 194 IS 14 A1 Duong, Diana A1 Vogel, Lauren YR 2022 UL http://www.cmaj.ca/content/194/14/E532.abstract