https://www.medrxiv.org/content/10.1....27.21261237v1

"the average time length for their serums to lose the detectable neutralizing activity was 198.3 days."
"BNT162b2-efficacy is likely diminished to under detection limit by 6-7 months post-1st shot"

Wouldn't be surprised if soon we start seeing "must be fully vaccinated within last __ months" for some restrictions. Will be interesting to see how it unfolds.