In general, you should wait six to eight weeks after completing the appropriate vaccination regimen to have a titer drawn. Having a titer drawn too early may result in a false negative since you'll still be in the process of developing antibodies.

Can titer tests be wrong?

CDC says antibody tests can be wrong

It can also take a while for certain people to develop antibodies after contracting SARS-CoV-2 — if an antibody test is conducted too soon, it could produce a false-negative result.

Are titers accurate?

Rabies vaccines do provide long-term protection, and the titer tests for rabies are also considered to be a very accurate measure of immunity.