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What happens if a dog misses a rabies shot?

Rabies booster study shows pets overdue for rabies vaccination are still protected

A research team at Kansas State University recently demonstrated that pets with out-of-date rabies vaccinations are still protected from the rabies virus—provided they receive a booster immediately after exposure. This study, appearing in the Journal of the American Veterinary Medical Association is the first of its kind to evaluate the rabies antibody levels in pets that are not up-to-date with their rabies boosters and may have significant implications for how such pets are handled after a potential exposure.

When a pet is bitten by a rabid animal, it’s an emotional and distressing time for owner and pet alike, often because owners worry that their pet will have to be euthanized. In the US, for suspected rabies exposures, animals that have never been vaccinated must be euthanized or quarantined long-term at the owner’s expense. Pets that are current with their vaccinations fare much better after a potential exposure: a rabies booster can be administered, and the pet can be released for home-monitoring.

However, for animals that have received at least one rabies vaccination but are past due for their rabies booster, the options are not as straightforward. Public health officials typically take a conservative stance and consider non-current animals to be “unvaccinated”, mandating that the animal be euthanized or quarantined after an exposure. Yet, because these out-of-date animals did receive a least one prior vaccination, a strong possibility still exists that protective antibodies may be circulating in their bloodstreams—raising questions over the necessity of such extreme measures for under-vaccinated pets.

In an effort to supply the missing clinical data to resolve this question, Moore and his colleagues tested the blood antibody levels in 74 dogs and 33 cats that were given a rabies booster either in response to a potential rabies exposure or for booster administration. Some of the animals were up-to-date on their vaccinations, while others were 1-4 years past-due for a booster. Using a rapid fluorescent focus inhibition test to monitor antibody levels, the researchers found that non-current pets quickly renewed their antibody production upon administration of the booster, generating levels of protection equal to (or even higher than) antibody levels generated by the up-to-date pets. Additionally, the rate of antibody production and median increase in level were often higher in the non-current pets than in the up-to-date population, indicating a vigorous immune response regardless of booster status. All pets achieved a recommended antibody level (≥ 0.5 IU/mL) after boosting. Irrespective of their vaccination history, cats responded rapidly to the booster vaccination.

These initial findings are intriguing and clearly show that even when owners do not adhere to the recommended vaccine schedule, their pet still may be protected from exposure to the rabies virus with an immediate booster, as long as the pet received a primary immunization in the past. After the initial vaccination, a pet’s immune system will generate neutralizing antibodies, which over time, can fall below the accepted, recommended level.

However, a booster can rapidly recharge the pet’s immune system, even if antibody levels have declined, indicating that active immunity against rabies remains for a lengthier period of time than that indicated by the vaccine’s expiration date.

This discovery clears the way for veterinarians and public health officials to re-evaluate and clarify the current post-exposure recommendations for treating pets with out-of-date vaccinations. The study involved a relatively small number of study animals, and just 12 known or suspected to have been exposed to rabid animals. However, the study authors recommend extension of the same treatment for up-to-date and non-current vaccinated animals after rabies exposure, with confirmatory blood tests to show an adequate response to the booster if reassurance is necessary. It should be noted that rabies vaccinations are usually required by law, and so unless recommendations change they should still be adhered to.

Contributed by Laura Baker, a GARC volunteer. The paper is entitled “Comparison of anamnestic responses to rabies vaccination in dogs and cats with current and out-of-date vaccination status” by Moore et al. and was published in JAVMA, Vol 246, No. 2, January 15, 2015.

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Ask Elizabeth: Need for Rabies Vaccination for Indoor Cats

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Q: My vet tells me that my indoor-only cat, Izzy, needs to be vaccinated for rabies. We live in an apartment in New York City and Izzy is never outside, so why does she need a rabies vaccine?

A: The simplest answer is that rabies vaccines are required by law for all cats and dogs over the age of six months in New York state — and many other states have similar requirements. But that’s probably not a very satisfying answer. Despite my early years running free on the farm, I now reside solely indoors, and I too have wondered why I need to be bothered with rabies vaccines. I’ll share what I’ve learned from my friends at the Feline Health Center.

Most importantly, rabies is a fatal disease for people or any animal unlucky enough to be exposed through a bite or scratch to the saliva of a rabid animal, so extra precautions must be taken to protect us all. Rabid animals don’t behave like normal animals — sometimes they’re overly friendly or abnormally aggressive. We’ve heard stories about rabid raccoons breaking through screens and coming indoors, and it’s quite common for bats, which have a high incidence of rabies, to find their way indoors. There’s nothing that I like better than chasing a bird or bat around the house, and I’ll bet that most of my feline brethren would agree. Bats can enter homes or apartments through small cracks.

There’s also always the chance, however small, that an indoor-only cat might sneak outdoors through an open window or door. Some of us become frightened and escape when we’re carried outdoors for, say, trips to the vet hospital, and I’ve heard about cats whose cars have been involved in accidents that left them suddenly free (cat carriers will prevent most of these accidental escapes). If I were unvaccinated or even overdue for my rabies booster (depending on how overdue I was) and came in contact with a rabid bat or other animal, the consequences could be quite severe. Each state has its own laws, and under the strictest laws, euthanasia might be recommended! If my owners didn’t agree to this, then a strict, six-month quarantine would be required, usually at a veterinary hospital-which can get very expensive.

While there is an expensive preventative series of shots that humans can receive to prevent disease after exposure to a rabid animal, no similar preventative protection exists for unvaccinated animals. However, if I were up-to-date on my rabies vaccination and then exposed to a rabid animal, I would simply get a rabies booster and a 10- to 45-day quarantine at home.

Similar consequences might occur if I were to bite someone. Even though we may be calm and loving at home, many cats (not me!) become frightened at the vet hospital and sometimes bite unexpectedly. Sometimes we bite children who frighten or hurt us, and sometimes we bite while playing. Bite wounds treated by a physician are typically reported to the health department, which may then request proof of rabies vaccination. If the owner can’t provide this proof, once again there may be repercussions for both owner and kitty, including a fine for having an unvaccinated animal; a recommendation that the cat be euthanized and tested for rabies, especially if the cat was ill; or a period of quarantine, for the cat. These penalties may seem overly severe, but remember that once the signs appear, there is no effective treatment for rabies. While the number of people dying from rabies in the United States is small (on average, one or two people per year die of rabies in this country), the number of fatalities is much higher in countries without strong vaccination and post-exposure programs. About 50,000 people die worldwide from rabies each year.

For all of the above reasons, I’m happy to put up with the inconvenience and bother of getting my rabies vaccine. The risks of skipping rabies vaccinations are just too great!

Rabies Vaccination

An animal can be considered immunized within 28 days after initial vaccination, when a peak rabies virus antibody titer is reached. An animal is considered currently vaccinated and immunized if the initial vaccination was administered at least 28 days previously or booster vaccinations have been administered in accordance with recommendations. Because a rapid anamnestic response is expected, an animal is considered currently vaccinated immediately after a booster vaccination.

Vaccination schedules

Vaccination of dogs, ferrets, and livestock can be started at no sooner than three months of age. Some cat vaccines can be given as early as two months of age. Regardless of the age of the animal at initial vaccination, a booster vaccination should be administered one year later.

Dogs, Cats, and Ferrets

All dogs, cats, and ferrets should be vaccinated and revaccinated against rabies according to product label directions. If a previously vaccinated animal is overdue for a booster, it should be revaccinated. Immediately following the booster, the animal is considered currently vaccinated and should be placed on a vaccination schedule according to the labeled duration of the vaccine used.


Consideration should be given to vaccinating livestock that are particularly valuable. Animals that have frequent contact with humans (e.g., in petting zoos, fairs, and other public exhibitions) and horses traveling interstate should be currently vaccinated against rabies.

Confined Animals


No parenteral rabies vaccines are licensed for use in wild animals or hybrids (i.e., the offspring of wild animals crossbred to domestic animals). The AVMA has recommended that wild animals or hybrids should not be kept as pets (14–17).

Maintained in Exhibits and in Zoological Parks

Captive mammals that are not completely excluded from all contact with rabies vectors can become infected. Moreover, wild animals might be incubating rabies when initially captured; therefore, wild-caught animals susceptible to rabies should be quarantined for a minimum of 6 months. Employees who work with animals at exhibits and in zoological parks should receive preexposure rabies vaccination. The use of pre- or postexposure rabies vaccinations for handlers who work with animals at such facilities might reduce the need for euthanasia of captive animals that expose handlers. Carnivores and bats should be housed in a manner that precludes direct contact with the public (12).

Serologic titers

Titers do not directly correlate with protection because other immunologic factors also play a role in preventing rabies, and the ability to measure and interpret those other factors are not well developed. Therefore, evidence of circulating rabies virus antibodies should not be used as a substitute for current vaccination in managing rabies exposures or determining the need for booster vaccinations in animals.

Interstate travel

Before interstate movement (including commonwealths and territories), dogs, cats, ferrets, and horses should be currently vaccinated against rabies. Animals in transit should be accompanied by a valid NASPHV form 51 pdf icon [PDF 13 KB] , Rabies Vaccination Certificate. When an interstate health certificate or certificate of veterinary inspection is required, it should contain the same rabies vaccination information as Form 51.

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