health
Titer test
What a titer does and does not measure
An antibody titer is a quantitative serology result, a dilution at which detectable antibody remains, reported as a number or as a positive/negative against a threshold. For canine distemper, adenovirus, and parvovirus, and for feline parvovirus, a positive titer correlates well with protective immunity. For rabies, titers are accepted for some international travel requirements but do not legally substitute for the rabies vaccine in most jurisdictions.
A titer measures circulating humoral immunity. Cellular immunity and immunologic memory may persist even when antibodies drop below the detectable threshold, a negative titer does not always mean the animal is unprotected.
When a titer is actually useful
- Confirming response to the initial puppy or kitten series (a single titer 2–4 weeks after the last shot).
- Adult dogs and cats whose owners want to extend re-vaccination intervals beyond three years for CDV, CAV-2, CPV-2, and FPV.
- Animals with a history of vaccine reactions, where avoiding unnecessary boosters is preferable.
- International travel that requires documented rabies serology (FAVN or RFFIT test).
Where titers do not apply
Titers are not useful for non-core vaccines whose protection is short-lived or correlates poorly with antibody levels, Bordetella, leptospirosis, Lyme, FeLV. For these, the duration of immunity is the basis for re-vaccination intervals, not a serology result.
Why it matters
A titer test is the bridge between two extremes, over-vaccinating on a calendar and under-vaccinating because 'they had their shots as a puppy'. For the four antigens it is validated for, it is the most defensible way to extend vaccine intervals while keeping immunity documented.
Frequently asked questions
- How much does a titer cost?
- In-clinic titers run roughly $40–$120 USD depending on antigen and lab. Send-out FAVN rabies titers for travel are typically $100–$300 USD. A multivalent in-clinic titer is more economical for routine wellness use.
- Can a titer replace my rabies vaccine?
- In most US states and many other jurisdictions, no, rabies is legally required regardless of titer. Some countries accept a documented titer for cross-border movement; verify the specific destination's rule before traveling.