From event page: At the moment of a faction change, the player’s personal progress is reset to zero. Test Tubes earned before the faction change are not taken into account in the player’s personal progress, and completed tasks are marked as incomplete. I may be wrong but I assume if you switch back to Immunes your progress will again reset to zero. I'm sorry that happened to you but make sure to read the event rules next time. You still have time to finish the missions if you grind. Good luck.