I think I may have found some clarification in the question and answer section through the “Sherpa” link which Rick Steves provides in his own Q & A (see at bottom under Question 8.)
I know that this will undoubtably change in the months to come, but as of right now (according to the Commission’s proposal) - Because the second dose of my primary vaccination was April 10, 2021 (with a subsequent booster on October 19, 2021), my primary vaccination would be recognized for 9 months until January 10, 2022. And, because that date extends (remarkably) to the applicable date of January 10, 2022, the booster would not be subject to a validity date. And, perhaps more importantly, it looks like the Commission is urging all member states to ensure additional vaccination for those whose certificates are approaching the 9 month limit. Let me know if you think I’m understanding this incorrectly, but it does seem to offer some clarification and hope for travelers.
“Question 8. The Commission proposes for the updates to the Recommendation apply as of 10 January 2022. Does it mean that the new validity rules, if agreed by the Council, would also apply as of that date?
To allow for sufficient time for the coordinated approach to be implemented, the Commission is indeed proposing that the updates to the common approach, including on the validity of vaccination certificates, should apply as of 10 January 2022.
For example, a vaccination certificate that indicates, as the date of vaccination with the second dose of a two-dose primary vaccination series, 15 May 2021 should be accepted until 15 February 2022. After that date, the holder can either travel on the basis of the vaccination certificate issued following the booster shot *(which would currently not be subject to a validity period at this stage)** or on the basis of a test certificate.*
A vaccination certificate which indicates, as the date of vaccination with the second dose of a two-dose primary vaccination series, 15 February 2021 should not be accepted when the validity rules start to apply on 10 January 2022 (as the 9 months already lapsed on 15 November 2021). As of 10 January 2022, the holder can travel on the basis of a test certificate.
Member States should immediately take all necessary steps to ensure access to vaccination for those population groups whose previously issued vaccination certificates approach the limit of 9 months”