Were there any studies that re-exposed ferrets at 3–12 months post-dose?

The short version: no ferret study in this retrieval rechallenged animals months after vaccination to test durable protection.

The single ferret COVID-19 vaccine study here challenged animals just 3 weeks after the booster dose and measured viral clearance only at 7 and 14 days post-challenge [1]. That is a short-term efficacy window, not a test of protection that lasts months. The study never brought the ferrets back for a second challenge later.

The broader animal evidence in this retrieval shows the same gap. A SARS-CoV vaccine study in ferrets using a modified vaccinia vector (MVA-S) found that neutralizing antibody responses were not protective and produced strong antibody-dependent enhancement effects [2], but that study also did not rechallenge after a delay. The rhesus macaque study that did rechallenge at 28 days post-infection found full protection [3], but that is a different species, a natural infection model, and still only a one-month interval.

No record here tested what happens when a vaccinated ferret faces the virus again 3, 6, or 12 months later. That is the design that would tell you whether protection wanes, holds, or turns harmful over time. It was not run.

My call: the evidence does not answer whether ferrets remain protected months after COVID-19 vaccination. Confidence: low, because the question was never tested in the studies retrieved.