Likely a lifetime. This question has many variables, but our clinical and scientific/experimental experience with these vaccines suggests that life-long immunity is likely. This is demonstrated by current recommendations of not needing booster doses, even when titers are zero in a person who has been fully vaccinated. These vaccines produce strong anamnestic responses in our bodies to confer longterm protection.
Not known for sure. Antibody to the vaccines can be detected for up to 15 years for both. The actual immunity to infection may be longer than that as cellular immunity may last longer.