This question came our way a few months ago: “Two city council members are challenging our TNR program. Specifically they are criticizing the fact that we don’t booster the 3-yr rabies vaccine after 1 yr as recommended by the AVMA. We’re working on our response but frankly all the recommendations from the USDA label to the new Rabies Compendium to our state department of public health rabies manual all say booster in one year. We are presenting information from the challenge studies that show the 3 yr rabies lasts quite a bit longer than 3 yrs with a single dose. Does anyone have any additional ideas for us?”
It turns out that the answer is pretty straightforward. It makes far more sense to have a population of spayed and neutered cats that have been vaccinated, than a breeding population that has not been vaccinated. A single live FVRCP/DHPP vaccine, and the rabies vaccine, produce effective and long-lasting immunity.
LIVE vaccines, which shelters should use wherever possible, produce immunity without requiring a booster. Revaccination is required for kittens and puppies because of maternal antibody, and recommended for adults for reasons that are frankly somewhat ill-defined but mostly involve compensating for errors in vaccine administration and storage, the theoretical possibility that a sick or immune-suppressed animal might not have mounted an adequate immune response, and the relatively fact that vaccines tend to provide limited protection against respiratory viruses. (If the first vaccine is not very effective for respiratory diseases, why would the second one be any better? I am still looking for a good answer to this…)
KILLED vaccines typically prime the immune response and do require a booster to provide protective immunity. This is one reason why killed vaccines are not recommended for shelters if a live vaccine is available. The rabies vaccines are an exception, however, because of the tremendous amount of effort that has gone into boosting their immunogenicity. So although rabies vaccines should certainly be boosted (by law and to protect the public), a single vaccine is still very useful and likely to produce long-lasting immunity in many or most animals.
A very interesting 2007 study showed that both live and (surprisingly!) killed FVRCP vaccines produced adequate and sustained immune responses in TNR cats, even though the cats were only vaccinated once, during conditions of stress and general anesthesia/surgery. Antibody levels were measured before vaccination and 10 weeks later. Notably, immunity to rabies jumped from 3% before vaccination to 98%, and from 33% to 90% for panleukopenia.
Many veterinarians and sheltering organizations now advocate the use of 3-year rabies vaccines only, and some shelters and clinics do not stock 1-year vaccines. The contents of the vaccines are often identical and only the labelling differs. There’s no real downside to using the 3-year vaccine as a 1-year vaccine, so long as the vaccination certificate clearly states that revaccination is required a year after the first vaccine. And it really makes sense to vaccinate feral cats with a 3-year vaccine at the time of TNR, as recommended by Operation Catnip and others.
- Response of feral cats to vaccination at the time of neutering, Fischer et al 2007 http://avmajournals.avma.org/doi/abs/10.2460/javma.230.1.52
- Rabies vaccination – 1-year or 3-year? http://chewonthis.maddiesfund.org/2016/05/rabies-vaccination-issues-in-tnrrtf-programs/