Spock, T'Pol and Jadzia were the only 'chief science officers' any Trek series has ever had.
Well, none explicitly had "Chief" in their titles, unlike Janeway on one of her past assignments. Still, one would assume that at least Spock had several other officers working under him in the Sciences Department.
Jadzia Dax probably didn't have any assistants originally, though. And whether NX-01 had any science crew worth mentioning (besides Sato)... Well, they launched on a supposed milk run in "Broken Bow" and never returned to replenish for the first two years. So possibly no scientists there. On the other hand, they stocked up with troops for Season 3, yet the total complement of the ship didn't seem to change. So did they offload some scientists? (They may also have offloaded engineers who were supposed to supervise the new warp drive on the maiden voyage, yet basically twiddled their thumbs for the next two years.)
And technically, Sulu seemed to be the "Chief Science Officer" of the ship in "Where No Man Has Gone Before", appearing as part of the gathering of department heads.
...Data, OTOH, was originally going to be the Ent-D's science officer. But the blue uniform didn't go well with his makeup. So they 'invented' the position of Ops and gave him a gold uniform.
As for the sources of this, I think there was something in the TNG Companion at least.
Timo Saloniemi