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Dog Owners Beware: Side Effects in the Melanoma Vaccine

President & Owner of Mise en Place Home, a Hawaii-based company.

Possible Side Effects of the Melanoma Vaccine

Possible Side Effects of the Melanoma Vaccine

My Dog Developed a Mysterious Limp

One day, my 11-year-old chocolate Labrador Retriever, Marley, returned from a visit from our neighborhood park with a noticeable limp in her left front paw. She wasn’t limping when she left for the park, so I initially thought that she must have stepped on something that had gotten lodged in her paw. I searched and felt the underside of her paw, in between her toes, and couldn’t seem to find anything. My next thought was that maybe she injured herself a bit running a little too hard from the excitement of being at the park and it would work itself out in a few days.

Now, Marley is a spry 11-year-old, and often while at the dog park, other dog-owner friends comment on how energetic she is for her age and how she shows no signs of slowing down. She is happy, lovable, and very food-motivated—often spinning her entire body due to the excitement of feeding. She is a dog that is agile and effortlessly jumps up and down from my bed each morning and night, which has a 27-inch clearance. Needless to say, Marley enjoys life.

My 11-Year-Old Lab, Marley.

My 11-Year-Old Lab, Marley.

Marley's Diagnosis

I monitored Marley’s limp for the following days and then into the next week or so. Unfortunately, her limp did not improve, so it was now time to take her to the veterinary clinic to uncover what the source of her limp could be. After X-rays were taken, it was discovered that Marley had melanoma in her front left paw and it had deteriorated the bone in the digit closest to her nailbed on her third toe.

Doctors informed me that the next step would be to amputate her entire toe to ensure complete removal of the melanoma. I wasn’t aware that melanoma could develop in dogs because I thought that their fur somehow protected them from this type of cancer. I also didn't realize that this type of cancer is especially aggressive in dogs.

Doctor’s assured me that the surgery was the right next step and that she would be able to “walk like her toe wasn’t even missing.” So, Marley completed her surgery and sure enough, she was walking normally a few days after surgery. Doctors also tested Marley to verify that the cancer had not spread to her lymph nodes, which gratefully, it had not.

The Melanoma Vaccine vs. Chemotherapy

The doctors suggested two post-treatment options to keep any future cancer at bay: the melanoma vaccine and chemotherapy. I was told that the melanoma vaccine has a good success rate with no side effects. Because the cancer hadn’t spread to her lymph nodes, Marley was a good candidate for this treatment. Chemotherapy actually has a better success rate than the melanoma vaccine but has known side effects similar to those experienced in human treatments, such as nausea, vomiting, diarrhea, and decreased appetite.

X-ray of Marley's paw.

X-ray of Marley's paw.

Deciding on the Appropriate Course of Treatment

In deciding the appropriate course of treatment for Marley, my guiding belief was not to add days to Marley’s life where she would be sick from the treatment side effects. I wanted to ensure that she would have a good quality of life in her remaining days, however many days that would be.

Melanoma Vaccination Protocol

Marley began her melanoma vaccine treatment in late March, which consisted of four initial shots given every two weeks followed by booster shots every six months for the next two years. In the state of Hawaii, there are only two veterinary internists that can administer the melanoma vaccine; luckily, they were both located on Oahu, which is the island that I live on.

Doctor’s assured me that the surgery was the right next step and that she would be able to “walk like her toe wasn’t even missing.”

Doctor’s assured me that the surgery was the right next step and that she would be able to “walk like her toe wasn’t even missing.”

When the Side Effects Started to Appear

Other than Marley hating the car ride to the internist and being scared of the loud sound of the shot when it was administered, as promised, there were no side effects. The shots were given in one of her hind legs, and they alternated legs between shots. However, after the second shot, I noticed that Marley seemed to be getting up slowly from lying down or from a sitting position, which was out of the ordinary for her.

When I took Marley in to have the third shot, I informed the internist of my observations. The internist said that there weren’t any known side effects with the melanoma vaccine, dismissing it and instructing me to inquire with Marley’s primary vet. Very shortly after the third shot, Marley started to have a noticeable limp in her front left leg, with obvious discomfort when she had to walk or get up from a sitting or lying down position. It appeared as though something was wrong with her front left leg, possibly at the shoulder area and coincidentally, this was the same leg where her toe had been amputated.

Scheduling a Recheck With the Vet

I really started to suspect that the melanoma vaccine was the source of Marley’s affliction. I searched the internet for any reported side effects of the vaccine but couldn’t find any reports or articles that were similar to Marley’s experience. I then took her back to the veterinary clinic that had done the toe amputation to uncover what was happening and why she was limping. Admittedly, when I arrived at the veterinary clinic, Marley was either anxious or excited or both and her limp seemed to disappear to the point that the vet couldn’t even tell which leg was affected.

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I told the vet my thoughts of how I believed that the melanoma vaccine was causing her to limp but again I was told that this wasn’t a known symptom of the vaccine. The vet asked me to return home and to videotape Marley to record her limping so that she could see the affliction. A few days later, I forwarded my recorded video to the vet and scheduled a follow-up visit.

"For weeks, Marley would lie around the house and not move."

Checking for Metastasis

The vet’s initial thoughts were that the cancer had spread to her shoulder area, which I was told was common and so X-rays were taken. When the results came back, they determined that there weren’t any signs of the cancer spreading but that Marley had arthritis in her front left paw and hip dysplasia (the hip dysplasia I had known about since she was about 1-year-old).

Carprofen for Pain Management

She was given 75 mg tablets of Rovera (carprofen) and I was also told that if Marley lost weight that this would also help her situation, as she weighed 86 pounds at that time. The next day I administered one pill with her food every 12 hours and it seemed to help. Her limp was not as severe, and she seemed to be moving a bit easier. I did call the vet to see if the dosage could be increased to match her weight, so 25 mg Rovera (carprofen) tablets were prescribed and I would split that tablet and give it to her at the same time as the 75 mg tablet. With that dosage, Marley started moving! The limp was still there but only noticeable if you were really looking for it and her happy spirit was returning.

Marley was becoming noticeably uncomfortable.

Marley was becoming noticeably uncomfortable.

The Side Effects Started to Intensify

Now that Marley had finally started feeling better and her mobility improved, it was again time to have her fourth and final melanoma vaccine shot. I battled over whether to go forward with it because I didn’t want to see Marley struggle again. However, I decided that since this was the final shot of the series, just to finish this out.

Marley Completed the Melanoma Series

Before Marley’s fourth shot was administered, I met with and updated the internist on Marley’s condition and informed her that Marley was currently taking Rovera as prescribed by the veterinary clinic. I again mentioned to the internist that I suspected that the vaccine was the source of her condition but that I had searched the internet and could not find anything similar to her symptoms. The internist replied, “Yes, it’s really not a reported side effect.” Marley left the room with the internist to have her final shot administered.

Marley Could Not Walk

The very next day following the shot, Marley could not walk. Marley would uncharacteristically lie around the house for hours and it was extremely difficult for her to walk herself outside to go to the bathroom or even eat (remember, she is highly food-motivated). She needed assistance getting up, and she would have to take two to three breaks when walking to either eat or go to the bathroom (the total distance for either is about 25 feet).

No longer able to leap on and off my bed, I slept with Marley on the floor so that I would know when she needed to get up and be able to lift her to her feet. There was no doubt in my mind that it was the melanoma vaccine causing her symptoms. The Rovera tablets were no longer helping at all. I called the vet that had prescribed the Rovera and asked her about the severity of her arthritis and hip dysplasia and if one or both were pre-existing conditions.

"I started having whispers in my mind about whether it was time to consider putting Marley down."

Communicating My Concerns to the Vet

The vet informed that she believed both were pre-existing and were mild. I said, “If you were to place it on a scale between 1 to 10, 10 being the worst, what would her status be?” She said, “It would be a 3.” I told the vet that Marley has never displayed any mobility issues from either the arthritis or the hip dysplasia. I told her again that I thought that the melanoma vaccine was either the cause or somehow exacerbating other pre-existing conditions.

This time, the vet did not dismiss me entirely. They said that Marley's symptoms did seem unusual and that I was very astute but again, there were no reported cases for these types of side effects. (In my mind, I was thinking, “Well, I’m reporting these side effects to you right now.”) The Rovera that had worked so well initially was now having zero impact. She said I could bring Marley into the clinic again for another observation, but I decided that Marley had been to so many doctor appointments in a short amount of time that I just wanted to see how she progressed outside of any further medical treatments.

Marley's Condition Deteriorated

For weeks, Marley would lie around the house and not move. Coincidentally, I had just left my job and didn’t have another job lined up, so I was able to tend to Marley throughout the day. I had to make her get up to go to the bathroom as she would not do so willingly due to the pain she was encountering. My only saving grace was that even though it was a struggle, she would still muster enough energy to want to eat, although she would have to take breaks before reaching her food bowl.

One week turned into two and two into three of Marley in this state. I reminded myself about my belief and goal—that the most important part of Marley’s treatments was for Marley to have a good life in her remaining days and not to arbitrarily add days to her life that were unpleasant. I started having whispers in my mind about whether it was time to consider putting Marley down.

Marley Spontaneously Improved

I had planned a trip to Vancouver for the last week of May and was debating whether to cancel it due to Marley’s condition. I had arranged for my cousin to watch Marley while I was away but given her condition, I didn’t think it was fair to have him watch her as she really needed around-the-clock care. He assured me that he could handle Marley’s care and urged me to go on my trip.

While in Vancouver, my cousin kept me updated on Marley’s condition, reporting that she spent most of her time lying on her bed with the air conditioner on. And then one day, my cousin texted me that he thought Marley was getting better and sent me a video of her. Sure enough, she was up and walking, with a noticeable limp but walking just the same. I was so happy to see her.

Marley today.

Marley today.

Marley Is a Different Dog Today

When I returned from Vancouver, Marley seemed better than when I had left. Although her limp was still present, she was up and walking. Now that I was home, I was able to watch her progress. Over the next three weeks, her limp seemed to get less noticeable with each passing day. Around late June, Marley finally returned to normal. Her mobility was restored—jumping on and off my bed, bugging me to go on walks and take her to the park, and spinning in circles just before her meals!

Now when I tell people about Marley’s experience, they can’t believe how well she has recovered and have returned to commenting on what a healthy and happy dog she is.


This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2019 Courtney Hannah

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