Table 1.

Analyses by arm.

Study question	Comparison
Among portal users, did portal message receipt alone increase the likelihood of influenza vaccine completion compared with control?	Compare percentage of vaccine completion among those randomized to receipt of portal messages versus those randomized to neither portal messages nor IVR calls (usual care). (Arm 2 vs 4)
Among portal users, did portal message receipt plus IVR call increase the likelihood of influenza vaccine completion compared with portal message alone?	Compare percentage of vaccine completion among those randomized to receipt of both portal messages and IVR calls versus those randomized to only portal messages. (Arm 1 vs 2)
Among portal users, did IVR call alone increase the likelihood of influenza vaccine completion compared with control?	Compare percentage of vaccine completion among those randomized to receipt of IVR calls versus those randomized to neither portal messages nor IVR calls (usual care). (Arm 3 vs 4)
Among those who do not use portals, did IVR call alone increase the likelihood of influenza vaccine completion compared with control?	Compare percentage of vaccine completion among those randomized to receipt of IVR calls versus those randomized to neither portal messages nor IVR calls (usual care). (Arm 5 vs 6)