The phrase "almost immediately then" is correct and usable in written English.
It can be used to indicate that something happened very soon after a previous event or statement, often to emphasize the quickness of the action.
Example: "The storm hit the coast, and almost immediately then, the power went out across the entire town."
Alternatives: "shortly thereafter" or "right after that".
Eyewitness memory begins to blur almost immediately, then continues to fade over time.
The mushrooms absorb the cooking fats almost immediately, then exude it after their water has been evaporated by the heat.
He went straight to Efremi's house, who almost immediately then went to withdraw £5,000 using the stolen cards.
On "Slow Blues," Coltrane lights into split-toned incantation almost immediately, then carries a steady improvisation forward for nearly the entire 11-and-a-half minutes of the track, interrupted only by a brief Tyner solo.
We had grown used not simply to seeing a goal scored but to seeing it over again almost immediately, then possibly a third time, in slow motion, to say nothing of being able to watch it later the same evening, and even the following day.
Normally, when we ingest glucose, the pancreatic beta cells release an initial burst of insulin almost immediately, then gradually release more insulin about 15 minutes later.
CMO Justin Mateen was suspended almost immediately (and then resigned) and then, earlier this month, the CEO Sean Rad abruptly resigned, taking role of President.
There he went to the Tichon Hadash progressive school in Tel Aviv - where he rejected Zionism almost immediately - then on to the Hebrew University of Jerusalem to study economics.
Your attention is diverted almost immediately and then diverted again.
Almost immediately Beccaria, then only 26 years of age, became an international celebrity.
"I asked NBC to fire that SOB or let me quit". Almost immediately, Roone Arledge, then president of ABC News, offered Brinkley another job, and he took it.
