Veterinary Vertex
Veterinary Vertex is a weekly podcast that takes you behind the scenes of the clinical and research discoveries published in the Journal of the American Veterinary Medical Association (JAVMA) and the American Journal of Veterinary Research (AJVR). Tune in to learn about cutting-edge veterinary research and gain in-depth insights you won’t find anywhere else. Come away with knowledge you can put to use in your own practice – along with a healthy dose of inspiration to remind you what you love about veterinary medicine.
Veterinary Vertex
Does Changing the Needle Matter? Evidence from a Canine Vaccination Trial
What if one of the most common vaccine rituals in small animal practice doesn’t help patients at all? We sit down with researchers Jane Sagaser and Dr. Rachael Kreisler to unpack a randomized clinical trial that tested whether replacing the needle after drawing up a canine subcutaneous vaccine improves comfort or outcomes. The result is a clear, practice-changing insight: no clinical benefit for dogs, and no reliable advantage detected by blinded injectors.
Together we explore how the team measured what matters—objective heart rate changes as a proxy for stress and a holistic, blinded reaction score at the moment of injection—while keeping the study grounded in real clinic workflows. We put long-standing beliefs under the microscope, tracing how dramatic but poorly documented images of bent needle tips shaped habits, and we connect the findings to human vaccine guidance that does not recommend needle swapping after vial puncture. Jane and Rachael also point out when replacement still makes sense: visible damage, contamination, or drops that compromise safety.
The conversation widens into sustainability, cost, and sharps volume, showing how small changes in protocol can reduce waste and needle-stick risk without sacrificing patient care. A surprising pattern pops up when the rabies vaccine is given second in the right rear limb, prompting new questions about site sensitivity, formulation effects, and the potential influence of temperature or tactile desensitization. We get candid about measurement challenges—from blood pressure cuffs to wearable heart rate sensors—and highlight the need for better species-ready tools to capture continuous physiologic data.
If you value evidence over habit, this is a guide to updating your standard operating procedures with confidence. You’ll hear practical strategies for critical appraisal, ideas for simple clinic-based studies, and a call to test assumptions rather than inherit them. Subscribe, share with your team, and leave a review to help more veterinary professionals find data that improves patient comfort, safety, and sustainability.
JAVMA article: https://doi.org/10.2460/javma.25.10.0661
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Welcome back to Veterinary Vertex, the AV Made Journal's podcast, where we delve into a behind-the-scenes look with manuscript authors. I'm editor-in-chief Lisa Fortier. Today, we're discussing how a randomized clinical trial finds no clinical benefit for needle replacement before sub Q vaccination in dogs with authors Jane Sagasar and Rachel Chrysler. Hey Jane and Repeat, Visitor of Rachel. Thanks again for being with us today. Thanks so much for having us. Thanks for having us. Yeah, I really like this topic. You know, it's uh it's not just about safety for veterinarians, but think of the environment. And the other thing I was taught early on in my internship, it's not just the cost of the needle. Somebody has to order it, somebody has to stock it, somebody has to empty the recycle or the uh needle bin. And uh so I just really, really love this topic and so grateful you guys brought it to us at JAVMA. Um, and Jane, before we dive in, share a little bit about the background and what brought you to investigating this idea of needle replacement.
SPEAKER_00:Yeah, absolutely. Um, so when I was an undergrad, I was working at an animal hospital as a veterinary assistant. And I noticed that there are certain practices like replacing needles that seem to be done differently by everybody. Um, you know, some veterinarians want to do it, some veterinarians don't, and same with technicians, seems like everybody has a bit of a different opinion on that. Um, so I became interested in clinical research, uh, not just about that, but just in general. And so when our vet school offered a summer research program for students to pursue doing a research project, I was definitely interested and knew I wanted to participate, especially in something that was clinically relevant. Um, so I was definitely intrigued by Dr. Chrysler's proposal to do this project specifically because I would have assumed that there was already research behind this because of how many people, um, how commonplace it is to replace needles before vaccination. Um, and so yeah, I wanted to work on that project and also because I've been always passionate about sustainability um and the environment and reducing waste as much as possible. So being able to work on a project where we're also, you know, investigating ways to reduce medical waste, that was very exciting for me.
SPEAKER_02:Yeah, it's it's actually so cool. Um, so this JAB article, as we said, discusses how uh pulling up the vaccine. So you might actually need to put saline in the lyophyllized vaccine, pull it up, and then inject the dog is clinically acceptable. Uh, tell us a little bit more about he how you and Rachel came up with this idea.
SPEAKER_00:Yeah, so um just anecdotally, it seems like so many people, like I said, have different opinions in the veterinary profession. Um, and not just opinions on this, but different justifications for why they change needles or don't change needles for vaccination. Um, and so the recent in vitro study that was published on needle sharpness showed that in a survey of veterinary professionals, 76% said that they do routinely change needles or replace needles for vaccination in dogs. Um, and so of that 76%, the majority were citing concerns of doling of the needle than affecting patient comfort. And so that study did ultimately find that needle sharpness is very minimally affected by puncture through a vial septum. And so what we wanted to do with our study ultimately was find out how the uh the one puncture through a vaccine vial is going to affect the dog's reaction itself. So in vivo. Um, and so something else that we saw online was that the CDC actually, in their vaccine administration guidelines, they recommend against changing needles in uh for human vaccinations. And that there's no, up to now, there's been no research in veterinary medicine um to back up, you know, any evidence to back up why this practice is so commonplace. So we wanted to be able to, you know, actually do this study to determine whether dogs are able to, you know, have a different reaction based on a replaced versus non-replaced needle. Um, and anecdotally, we've also heard just from colleagues, super commonly, you've probably heard this too, or maybe you think it yourself, that uh when you change the needle, some people claim that it does, uh, or when you replace the needle, that it feels like it goes in more easily when you go to vaccinate an animal, or that the, you know, they can just tell the difference. So that's a claim that we wanted to be able to test as well to see if um, you know, people can actually truly discern a difference between a replaced and a non-replaced needle.
SPEAKER_02:Really good points. How did you and Rachel design the study to assess and uh evaluate those questions that you just brought up?
SPEAKER_00:Yeah, so we um discussed quite a bit together, uh, you know, in a group with the other researchers as well, to see, you know, what would be the best ways to um evaluate dog reactivity, um, not only in the sense of like how the um, you know, heart rate going up. So we wanted to test, you know, sympathetic nervous system, what's going on there, but also their actual reactivity when being punctured by the needle itself. So we um, you know, we spent a lot of time discussing that and looking at existing literature. And then most importantly, our pilot studies are really how we landed on, you know, analyzing the heart rate as well as the holistic reaction score.
SPEAKER_02:How did you test the injector, the injector's reaction to like is that dull or not?
SPEAKER_00:Yeah, so for uh each dog in the study, um we had them receiving two vaccines. And so with one of the vaccines, the needle was the replaced and one was the non-replaced. And so the injector was blinded as to which was which. Um, and so we had them compare after doing both vaccines on the same dog. We asked them, you know, which needle did you think was the one that was replaced.
SPEAKER_02:So, what were the most important findings uh that supported your conclusions?
SPEAKER_01:Well, I thought that it was uh very helpful to have looked at uh several different perspectives. So um I think that, you know, seeing no difference. So it was really the three together, seeing no difference in um an objective measure of heart rate, no difference in this uh blindly rated holistic subjective uh uh rating of the dog's reaction to the puncture and not having the injectors, uh most of whom did not want to make a guess, uh, but or many of whom I guess did not want to make a guess. And um, and then uh those who uh get uh looking at those uh also who did, uh being unable to tell the difference. I think for us that provided pretty good uh evidence that we really weren't seeing anything that was clinically meaningful. And this didn't really surprise us after this the in um vitro study, because um the the biggest uh defect that we saw in the the worst affected um needle with the gross defects was about a third of what um humans are uh able to tell the difference of. So of course we can ask a human, you know, how much did this hurt? Or can you tell the difference between this needle and that needle? And so uh these these findings were very congruent with what we'd seen um uh outside of the dogs as well.
SPEAKER_02:It's an elegant study. It's quite simple and it's elegant and it's a myth buster. So what could be better? Thank you. Are there any times in clinical practice that replacing a needle would be appropriate?
SPEAKER_01:Certainly, I would say if there's any type of you know damage, uh you drop the needle, you uh it impacts the side of the vial um sort of strongly. If you have any concerns about contamination, um beyond, yeah, um, those are so we're never saying never do it, just don't do it as part of routine practice. Um so that's uh but we, you know, in in the discussion, we we did look into sort of um concerns about uh just sort of environmental contamination passing through a uh a vaccine bile septum. And um, there wasn't a lot of literature on this as well. But if you think about everything you're passing through on your way in um into the dog, uh and and we're not taught to prep the skin surface. And in fact, um laboratory animal manuals recommend against prepping the skin surface. Uh, and we don't see um, you know, we had over 10,000 vaccine events in our records and had no records of abscess. Um, you know, and it's certainly not something I've encountered in other environments either, uh, in you know, for small animals. So we we felt pretty confident that routine use um was not a significant uh risk for um injection site uh contamination.
SPEAKER_02:Yeah, all makes sense, you know, and at least in horses, they hate that cold alcohol applied to them. So now you've stressed the animal out and then you're gonna stick a needle in them. And it's just just not necessary. Rachel, we heard a little bit about Jane's uh journey into this topic. What about you? What sparked your interest in needle replacement?
SPEAKER_01:So what sparked my my interest before even before you know for that first study was uh I signed up to give vaccines to humans during the COVID pandemic when they were sort of recruiting everyone who could stick a needle in in anything. And um, and that's where I first encountered this uh message from the CDC that changing the needle after drawing out the vaccine was not indicated. Uh, and I was like, huh, oh why do we do this for animals then? Uh and I really went down a rabbit hole. Um, and uh and you know, I think a lot of this ends up originating way back in the 90s, which to me does not seem that long ago, but apparently is quite a long time ago. Uh and the American Diabetes Association had sort of been like, you know, if you're gonna reuse your own needle um to give yourself insulin syringes, as long as you kind of follow some general guidelines, that's probably okay. And Big Needle was sort of like having none of that. So they came up with these scared straight images that show what happened to a needle after reuse. They put them in the boxes of syringes they were selling to people, and these just really got embedded in the public imagination. And I'm going to assume pretty much all of us have seen these at one point or another, you know, these dramatically deformed um needle tips. Although, of course, everything looks scary under a scanning electron microscope, but these were never published with any information. Well, one, they were never published. They were never in the peer-reviewed literature. There was no information about the needle size, there was no information about um uh what magnification it was, uh, what technique had been used in in terms of this um of this reuse. Uh, and and so um uh the and it and it was actually uh even further down the rabbit hole going into the uh Internet Archive Wayback Machine, uh, where you can find uh you know things that no longer uh websites that no longer exist on uh on the internet. And there was even some citizen science done back in the day. There was a professor who um had diabetes and um uh also had access to a colleague with a scanning electron microscope, and the professor was sort of like, huh, well, that's weird because I reuse my my needles uh and I don't feel like you know I can really tell the difference. And so they tried to reproduce these images again contemporaneously uh and and weren't able to without a sort of extreme, you know, sort of stabbing or dropping it on the on a table or something like that. And so uh unfortunately the the uh internet archive only has the text and not the images, but um it led us to do our first study, uh looking at uh again what happens to sort of just passage through septum, which of course are not the same as as human tissue, and uh really seeing that it's not as dramatic as uh we may have been led to believe, at least for the use uh for our purposes of um drawing up the vaccine. So scared straight doesn't work. Um and isn't scared straight a comedy? I it probably is. Um I mostly again uh speaking of the 90s and you know, the scary images about what happens on drugs and things like that. So I guess maybe but I know that I've seen them in presentations where it's like, here's what happens to the needle when you reuse it, and don't ever reuse the needle.
SPEAKER_02:But uh yeah, I I love this. So and I encourage people to challenge dogma or eminence-based sort of things too. So, how do your findings and how do you encourage clinicians to and students to think more critically about tradition?
SPEAKER_01:Uh so I do teach um critical appraisal of veterinary literature uh at uh at Midwestern University. And um, I guess what I would say is um pay attention to that voice that goes, huh? Uh, you know, and and uh and and you know, just sort of as you're going about your day, you've pointed out that this was a pretty simple study. A lot of the studies I do are very simple. Um, and there are things that you can do, you know, uh in your own clinic. You you can um you know do them. I I sometimes present my findings at conferences and I say, wow, go ahead. If you don't think this is your experience, test it. And you know what? If if it's different, let me know. Because nothing gets an epidemiologist more excited than a different pattern of disease or you know, whatever it is that we're looking at, because now we can know a little bit of something about maybe why it happens. So um, so I so I actually would love people to go and try to prove me wrong. Uh, you know, use use robust methods, but um, you know, maybe we can find a difference. So maybe it matters, you know, for a subpopulation I I I didn't enroll enough of, or maybe it uh it matters um in some environments rather than others. That's that would be so exciting because then we would have some insight into to what's really going on.
SPEAKER_02:Yeah, I think you just uh answered or at least teed up my next question of uh every study we do leads to more questions. Uh so what do you think are the most important things to address next in this area of needles or vaccines?
SPEAKER_00:One thing that was really interesting in our study was we saw that um, because we did standardize that when when rabies was given, it was always the uh right rear limb and the DHPP vaccine was always the front right limb. Um and so since that was standardized, we did see a pattern of when the uh rabies vaccine was given, I believe second. And obviously, like was it first that it was the order was randomized.
SPEAKER_01:Well, when because we right, because we oh sorry, no, no, no, you're right. Sorry, you're saying the findings, not the methods. Sorry, the order given was randomized, but the findings are exactly what you're going to say. Exactly.
SPEAKER_00:So when we um, you know, we're looking at the data and we saw that when rabies vaccine was given second, because again, it was randomized as Dr. Pleitzer was saying, it wasn't always giving given second, but when it was, we found that um that specifically uh we did see more of an increased heart rate in the dogs versus any other time or any other order of vaccine. Um and again, not depending on whether it was replaced needle or non-replaced needle, but just specifically the rabies vaccine second, we saw um the a statistically significant change in heart rate. So um, it's interesting. It that kind of leads us to wonder, you know, does it have to do with where we're placing the vaccine? Do they not like that right rear um area, or could it have to do with the rabies vaccine itself?
SPEAKER_02:Yeah, that is interesting. Um yeah, it's not wind up, obviously, because it was randomized whether it was first or second. Are were all the vaccines cold? I always wonder about that when I vaccinate my dogs and horses. Yes.
SPEAKER_01:Yeah, they should all have been about the same temperature. They were kept in a uh refrigerator up until uh just before the honest broker uh drove drew them up and and handed uh handed them off in the order they were to be given.
SPEAKER_02:And I wonder if that would be an area to investigate. I have two friends that are on GLP1, and they both swear that it's less painful if it's at room temperature.
SPEAKER_01:I think they're not very good at injecting themselves, but I'm also intrigued to find out if some of the things that I do actually work. Uh so I try to desensitize the area by, you know, sort of touching and uh and then oop, there it went. But I have no more evidence uh for that working uh than I do for for changing the needle. Uh it's a technique that is used in human medicine, but the the evidence is not completely clear-cut about whether that works as well. Although I will say when I get injections and you know, I've gotten different vaccines and whatnot at different times, I feel like that helps me. But uh yeah, we'd have more things to more things to check.
SPEAKER_02:When you do a study, there's always like, oh, I wish I had this or I wish this was better. Uh, what methodological improvements or other technologies could have helped you in this study?
SPEAKER_00:We definitely tried different ways because we originally weren't sure if we were going to be measuring blood pressure or heart rate as our objective measurement. And so in our pilot studies, we tried, you know, doing blood pressure monitoring. We tried monitoring heart rate, um, obviously manually, but then also we tried actually with an Apple Watch. So we tried with, you know, putting an apple rock, an Apple Watch around the dog's arm to see if that would be good for monitoring heart rate. Didn't the literature is Lenaro? Um, but we found that it was difficult considering how many different sizes of dogs we would be having in our study. Um, and so we ended up going with um a polar monitor, polar heart rate monitor that's meant for humans, of course. And there are studies showing its efficacy for continuous heart rate monitoring in dogs. Um, but yeah, I think even with that, and it was mostly effective. Uh a lot of our data, unfortunately, um, couldn't be used with that heart rate monitor. Not a lot, a lot of it, but a good chunk of it we had to not use for our heart rate um data just because it wasn't completely continuous or um, you know, it it wasn't reading for whatever reason. Um and we tried to mitigate that with an ultrasound gel and you know, just trying to get that good fit on the dogs. But given that it's not made for dogs, it wasn't perfect. So I think that would be a great next step or next type of technology would be uh continuous heart rate monitoring for for dogs and cats. Yeah.
SPEAKER_01:Though just to be clear, with a negative finding, we were fully powered. Uh we knew that uh the heart rate, um, the polar monitors were imperfect for this uh use. And so we did reach full enrollment for the usable heart rate uh monitor, uh heart rate readings.
SPEAKER_02:Somebody mentioned earlier uh that the CDC has recommendations on needle replacement. Do you see this work as influencing policy for veterinarians?
SPEAKER_01:Unfortunately, CDC didn't provide any citation or rationale for why they don't recommend changing. Uh so unfortunately, um uh we can't act ACIP now uh what they were thinking, uh, since there's been quite a lot of change over there. But um we we speculated, because of course they're quite interested in human um health and safety, that it was my guess would have been that it's due to the uh risk for needle stick injury uh when folks change the needle.
SPEAKER_02:How about for veterinary medicine? Do you see this influencing guidelines, protocols, or policy? Great question.
SPEAKER_01:Um, so it's already uh in our draft of the uh soon-to-be released uh Association uh of shelter veterinarians uh shelter vaccine guidelines that should be coming out later this year. So um both the in vitro and in vivo study are are referenced in there to support not changing the needle.
SPEAKER_02:Before we wrap up, let's have a little fun. Uh Rachel, what's one belief or habit in veterinary medicine you'd love to see gently retired?
SPEAKER_01:Uh, I still encounter veterinary professionals who routinely apply caro syrup to the gums of young animals after surgery. Um and um it's a technique that doesn't work, but it's also for a condition that's not appearing to happen routinely. So uh I would I would love to um stop that. Or again, if you think it's something that you do see a difference, great, let's study it, let's figure out what's different. But at least um in one of uh a couple of my earliest papers, uh we looked at actually kittens are far more likely, uh and these when I talk about kittens, I mean kittens aged 8 to 16 weeks, far more likely to become hyperglycemic. Uh over half become hyperglycemic and in fact after surgery. And none that we measured in in 75 kittens became hypoglycemic. Um and then we, of course, looked at the next step, which is uh half the kittens got uh caro syrup and the other half didn't. And uh we did not see any difference in um blood glucose levels uh between the treatment and control group. And we actually were not surprised because we had done the math uh beforehand and had done a pilot study where we looked at what is the absolute maximum amount of caro syrup you can actually get on these, you know, we used different brands of cotton swabs and like really loaded them up and sticking them in the buccal um pouch of the kitten and how much can we really load up on these guys? And um, we did the math, and even if 100% of that was bioavailable, uh, which of course it's not, but even if it was, it it wouldn't be enough to to raise the blood glucose by a meaningful amount. So um it, you know, we still were glad to done this, you know, to done the study, but it kind of confirmed what the math had uh suggested to us. So unfortunately, again, I think it's one of the areas where um clinical practice intersects with the feelings you get that you you're demonstrating to yourself and your colleagues that you really care, which is so important, where veterinarians and veterinary professionals are caring people. And um I think it's just really hard to um convince it people's feelings about um something that makes them feel good and makes them you know feel like they are doing a good thing for an animal, that they are demonstrating that they're good doctors or good techs. Uh so um I've been fighting this fight for uh uh quite a while now.
SPEAKER_02:And um I'm not sure I'm winning, but yeah, I remember giving a talk at a human conference on microfracture and articular cartilage repair. And I asked for a show of hands before I gave this talk that, you know, when you put those slides together, you you spend days making sure you're up to date on clinical research. And I asked for a show of hands and then I gave my talk, and it basically though the title of the talk was put your all down. The all is the thing you do use to make microfracture holes, all of them. And so the talk basically was how detrimental microfracture is. And at the end of the talk, I asked for a show of hands and how many people were still going to do microfracture, and almost all of them still raised their hand. I was because they still thought it worked, despite all that evidence, they still believed in their hands that it worked.
SPEAKER_01:Yes, the in my hands is a very uh challenging uh uh sort of term to overcome. But you know, every time I presented these findings, I said, look, if you think this is working or you're seeing something else, that is actually so exciting. Show me, tell me, and we'll figure out what's different. Um, you know, uh uh I haven't had anyone reach out yet.
SPEAKER_02:And Jane, over to you. What is a small thing at work or outside of work uh that reliably makes your day better?
SPEAKER_00:Well, for me, definitely coming home and seeing my cats and my foster kitten, one of my cats, Alfie, is right here. Decided to make an appearance. Um, but yeah, they always just bring me so much joy. And even after a tough day, they remind me why I'm in this profession. Well, Rachel and Jane, thanks again for being here with us today.
SPEAKER_02:Thank you so much for having me. Great, thank you so much. For our listeners and viewers, you can read Jane and Rachel's article in Javma. I'm Lisa Fortier. Be sure to tune in next week for another episode of the Veterinary Vertex. And don't forget to leave us a rating and review on Apple Podcasts or wherever you listen.
