[Spirochete]

Also, Venona was almost entirely from 42 to 45, with a very few as late as 48.

It lasted until 1980 according to Wikipedia.

[Sherman Logan]

The messages in question were mostly sent from 42 to 45, with a few as late as 48, like I said.

Attempts to decrypt them continues as late as 1980, but no new messages were intercepted after 48.

The whole program was due to the Reds screwing up and using duplicate one-time pads. Once they figured this out, they went back to pads used only once and decryption again became impossible.