I’m surprised there hasn’t already been a flood of responses. Perhaps many folks with authoritative knowledge will chime in at some point. It looks like current Italian policies are in effect thru March 31, before your planned trip, but maybe not soon enough to make a comfortable decision. The 6 month deadline appears to be aimed at getting non-vaccinated Italians vaccinated, but visitors could get caught up in all this.
I can’t guarantee that I’m seeing this right, but looking at the U.S. Embassy in Rome Website - which, sadly, advises against travel to Italy at the moment (but that’s another story) - it describes the Super Green Pass and the “Basic” Green Pass. That’s their bold and quotation mark indicators, not mine. Super means you’re fully vaccinated, and can eat inside or outside at restaurants, and stay in lodging and ride public transportation. Basic simply means you’ve tested negative, and can get into hairdressers, banks, post offices, and stores. Then it says that the Green Pass, without distinguishing between Super or Basic, is being reduced from 9 months validity to 6 months, effective Feb. 1, 2022 thru March 31, 2022.
My take on it (again, no guarantee) is that the Basic status is now just good for 6 months. I’m interpreting the Embassy Website as by saying Green Pass, it means the basic one, as opposed to the Super Green Pass. So then, Super, meaning vaccinated, is good for 9 months. If that’s correct, it would seem that, come February, you’re still good for 9 months from the date of your last booster shot. And come April 1, 2022, there may be new policies.
Here’s the Website link, for what it’s worth: https://it.usembassy.gov/covid-19-information/ It also says to go to the Italian Ministry of Health’s Website, and provides its link. Unfortunately, other than the words “EU Digital COVID Certificate” and “Green Pass,” everything else on that Website is all in Italian!