Three surprising facts about the rabies vaccine

Whenever a patient presents with an animal bite, it is always a time when you are desperately hoping that the animal: has a known vaccination history, or can be quarantined for 10 days to determine whether or not it begins to show signs and symptoms of rabies.¹

Rabies vaccines can be painful and the immunoglobulin administration can involve a lot of needles at one time for the patient. The patient also has to come back at specific times to abide by the vaccination schedule, which can become quite expensive and inconvenient. But unfortunately, during those dreaded times when the animal is unknown and the attack is unprovoked, rabies shots are in order.

So, when my hospital informed me a couple of months ago that they were no longer requiring the fifth post-exposure vaccination, I was surprised and wanted to know what had changed in the protocol. I decided to check CDC guidelines on the matter, and I learned a few other things along the way.

Fact 1: The change in guidelines from five vaccinations to four vaccinations occurred in 2009

It was determined that four vaccines provided as safe coverage as the five vaccine schedule, and therefore the fifth was not necessary.

Although it is still recommended that patients get vaccinated on days 0, 3, 7, and 14, day 28 is only recommended for immunocompromised patients.² I do not know why my hospital decided to make the switch when it did, but my guess is that it was to ensure proper coverage of any patient that would have an unknown compromised immune system.

Fact 2: Small rodents are almost never found to transmit rabies to humans

“Small rodents (like squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats, and mice) and lagomorphs including rabbits and hares are almost never found to be infected with rabies and have not been known to transmit rabies to humans,” per the CDC website.

Racoons, skunks, foxes, coyotes, and bats continue to be the reservoir for rabies, serving to infect other mammals and humans as well.³ I was very surprised by this, as I have had several patients come in for rabies concern after being bitten by rats.

Keep in mind that although rabies is not a concern for the above listed animals, you do need to ensure proper prophylactic antibiotic coverage to prevent infection, as animal saliva is laden with bacteria. (I will also go on to mention that I have gotten a trivia question right after learning what a lagomorph was from this research.)

Fact 3: Side effects from the vaccine are common

I have had several people come back to the ED, because they were experiencing side effects that they attributed to the animal bite or the onset of rabies, when in actuality it was an adverse drug reaction to the vaccine.

Per the CDC, a localized reaction to the injection site is experienced in as many as  30% to 74% of people that receive the vaccine, and as many as 5% to 40% of patients can experience flu-like symptoms such as headache, myalgias, nausea, vomiting, and diarrhea.

In rare instances, patients can experience fever, joint pain, and hives.¹ I always make sure to give my patients proper counseling on what to expect when they get the vaccine, and I always give them literature about the vaccine to read at home.

While administering the rabies vaccines still remains low on my list of favorite things to do in the ED, becoming more educated about when the vaccine is warranted and what to expect from it has helped make the ordeal a little easier for both staff and patients alike.

Jillian Knowles, MMS, PA-C, is an emergency medicine physician assistant in the Philadelphia area.