Are Pet Vaccines “Safe and Effective”? Part I

The Feline Distemper Vaccine and Chronic Kidney Disease in Cats

Introduction

Because of the Covid-19 vaccine scandal, many people are waking up to the stark reality that vaccines labeled “safe and effective” often are anything but.  More Americans than ever before are beginning to question the wisdom of blindly following the advice of self-proclaimed experts on not just the Covid-19 vaccines but all vaccines, for humans as well as animals.

In this context, questions about the safety and efficacy of vaccines for cats and dogs have come up repeatedly in the comments section here as well as on other Substack pages.¹ It seems to be a topic of great interest to readers.    

Last spring, I made a commitment to tackle the issue as my time permitted.

Then, life happened.  My elderly father passed away. Priorities changed.  Suddenly I found myself with little free time to spare for researching and writing Substack articles.

At long last, I have been able to clear the deck enough to make room once again for some citizen journalism.

This article is the first installment in a planned series of reports in which I will attempt to review the published research on the safety and efficacy of commonly administered vaccines for cats and dogs.    

While I remain focused on the health and safety of children, I do not view animal vaccination and child vaccination as being unrelated.  In fact, what is happening to our pets seems to closely mirror that which is happening to our nation’s children. 

It is not my intention with this series to try to tell pet owners what to think or how to care for your animals.  I will include links to all the studies I cite in the hope that each of you will spend some time reviewing those studies for yourselves. 

Please post your own experiences with your pets in the Comments Section at the end of this article.  Please also let me know if you believe that I have misinterpreted any published research or overlooked relevant studies.

In addition, if you find this report informative, consider sharing it with other cat lovers in your circle.  I am not active on social media and have no way of promoting my Substack articles, all of which I write on a volunteer basis, other than through you.

Note:  While I have tried to be succinct, this report is not a quick read.  So, pour yourself a cup a coffee. Then, if you have one, call your furry feline to your lap and get comfortable.

Willow’s Story

This is Willow.  I adopted her from a shelter in 2002.  She was a year old at the time.  Other than her age, I knew only three things about her:

1) She had been given up by her previous owner.

2) She was spayed.

3) She was vaccinated against rabies as well as distemper. 

Along with being spayed/neutered, all shelter cats were required to be “up-to-date” on their vaccines before they could be placed for adoption.

After I adopted her, Willow lived indoors for the rest of her life.  She received no additional vaccines.  She ate regular cat food – not the most expensive brand, but not the cheapest, either.  She was somewhat overweight but otherwise healthy. She was a happy little camper, and she made me happy.    

Then, in 2014, my husband and I noticed that Willow suddenly seemed to be drinking water all the time –lots of it. Every time we turned around, her fresh bowl of water was nearly empty.  We knew enough about cats to know that this was not normal. 

In fact, excessive thirst is often the first sign of illness in cats.

A quick trip to the vet revealed the sad news.  Our Willow was suffering from chronic kidney disease.  There was no cure.  The recommended treatment was a special diet low in protein and phosphorus. We could also give Willow fluids under her skin.  

Regardless, her disease was destined to kill her within two years.

We fed Willow the recommended special diet and, as her disease progressed, I learned to give her fluids subcutaneously.  It was painful for her and extremely uncomfortable for me. 

Despite our best efforts to help sustain her, Willow gradually lost her appetite.  She also vomited regularly.  We were constantly cleaning up after her.  Her body weight plummeted. She felt like a rag doll in my arms.

During Willow’s final weeks, she seemed to want just to sit alone next to an open window in our living room and take in the fresh air. 

Then one morning, Willow woke up crying out in terrible pain.  We rushed her to the vet, who promptly informed us that there was nothing more to be done for her. Our little Willow was dying.  It was time to bring an end to her suffering, which we did.  

How Many Willows?

Chronic Kidney Disease (CKD) in cats is defined as “a prolonged process marked by irreversible loss of kidney function, usually without an identifiable cause.”² Healthy kidneys perform many important functions, including filtering the blood and making urine.  Kidney disease can result in a variety of serious health problems for a cat. Waste products and other compounds in the bloodstream that are normally removed or regulated by the kidneys can build up, causing the cat to feel sick, suffer lethargy, and lose weight.  Cats with kidney disease may also urinate more frequently, in greater volume, and drink extra water to compensate.   

As the disease progresses, cats commonly suffer many complications, including hypertension, low potassium, anemia, and numerous other blood disorders. 

So, how common is CKD in cats?  Just how many Willows are there out there?

The short answer is…nobody knows.  Scientists report that CKD is the most common metabolic disease in domesticated cats.  They also agree that CKD has been diagnosed increasingly over the past three decades, particularly in older cats.  In addition, they note that CKD is now at least twice as common in cats as dogs.³

Anecdotally, veterinarians report seeing lots of CKD in their practices.

Yet, official estimates of the prevalence of CKD in cats vary widely. Researchers who looked at data from the Purdue Veterinary Medical Database estimated that the overall prevalence of feline CKD increased from 0.04 percent in the 1980s to 0.2 percent in 1990s to one percent by the 2000s.⁴ A study by Colorado State University of 18,938 cats from 1992 through 2001 found a diagnosis of chronic kidney failure in 3.6 percent cats.⁵

Meanwhile, across the pond, where similar veterinary medicine is practiced, a U.K. study published in 2015 found kidney disorders to be the most frequently identified cause of mortality in cats five years and older, accounting for 13.6 percent of all deaths in that age group.⁶ A Swedish study of insured cats up to 13 years of age, covering the period 1999-2006, found disorders of the kidneys or ureters to be the most common cause of mortality, accounting for 7 percent of deaths.⁷

By stark contrast, a study out of North Carolina State University, published in 2013 in the Journal of Feline Medicine and Surgery, found a stunning 50 percent prevalence of CKD for domesticated cats in one randomly selected feline-only practice in the U.S. The researchers reported that even in the youngest age group, consisting of cats from birth to age five, 37.5 percent showed markers of chronic kidney disease.⁸ The researchers were unable to account for the difference in their findings relative to previous studies. They emphasized that their study design had included more comprehensive testing for kidney disease, which enabled the detection of many Stage 1 cases that are often overlooked in other studies.  Still, this alone could not explain the disparity.

So, how prevalent is CKD among cats in the U.S. today?  Is the true number 3 percent, 7 percent, 13 percent, or 50 percent? There seems to be no sense of urgency in the field of veterinary medicine to answer this fundamental question.

In fact, this is a common theme throughout the published research on pet health.  Apparently, there is no strong financial incentive for anyone to quantify the incidence and prevalence of diseases that commonly afflict cats and dogs. Therefore, government and private institutions don’t want to pay for these studies. 

For those who make their living in or otherwise profit from veterinary medicine, it may also be counterproductive to do so.  This is especially true if widely administered vaccines turn out to be a major cause of serious illness in animals. Pet vaccines are to veterinary medicine what childhood vaccines are to pediatricians – the bread that pays the rent and keeps the lights on.  Needless to say, vaccines that are either required by law or universally recommended also are highly lucrative for the pharmaceutical companies.

Yet, for cats and those who love them, the question could not be more urgent, because there is reason to suspect that many, if not most, cases of CKD in cats today are caused by the distemper vaccine.  If so, they are preventable, and the terrible suffering of potentially millions of our beloved pets is unnecessary.

Crandell-Rees

In the 1970s, the Crandell-Rees feline kidney (CRFK) cell line was discovered to successfully propagate various feline viruses, including feline panleukopenia, the virus that causes what is commonly referred to as distemper. 

Distemper is a highly contagious virus in cats.  The disease affects the blood cells in the intestinal tract, bone marrow, and stem cells. Symptoms of feline distemper range from mild to severe.  They may include lethargy, vomiting, diarrhea, fever, dehydration, weight loss, and in the most severe cases, death.  Infected felines usually are sick for approximately one week but can continue to shed the virus for up to six weeks.  Those that survive the infection develop lifelong immunity and can no longer transmit the virus.

Most cats that become very sick with distemper are under one year old.⁹ The fatality rate for infected newborn kittens that do not receive timely treatment – in the form of good nutrition, fluid replacement, and antibiotics to ward off opportunistic infection¹⁰ – may be as high as 90 percent.¹¹ Even with timely intervention, distemper in kittens is often fatal.  By contrast, older cats that are otherwise healthy usually experience only mild symptoms.¹²

We are told that, in the past, this virus was a common cause of feline death.  The distemper shot is credited with greatly reducing its prevalence.¹³ However, just how prevalent it was in the past and by what percentage the vaccine has reduced it appears to be a complete mystery.  I was unable to locate a single published study on the incidence or prevalence of feline distemper in the U.S.  (If any of my readers are able to locate such studies, kindly post the links in the Comments section below.)  Studies outside the U.S. also are few and far between.  Once again, there seems to be little incentive for anyone to fund this research.  

In any case, FVRCP is a combination vaccine that protects against three different viruses, of which distemper is the one considered by far the most threatening to cats.  While the FVRCP vaccine is not required by law, it is universally recommended. 

FVRCP is not a one-and-done vaccine.  The American Association of Feline Practitioners recommends that shelter kittens receive their first dose as early as four weeks of age and additional doses every two weeks, until 16 to 20 weeks of age, followed by a booster shot at six months, with additional boosters every three years thereafter.¹⁴ Many vets encourage even more frequent vaccination in adulthood. ¹⁵

The celebrated CRFK cell line was deemed a valuable tool in the production of this vaccine. However, from the outset, there was a problem.  Scientists who studied the CRFK cell line noted that during virus purification, it was not possible to remove all CRFK cell proteins. Thus, they concluded, it was likely that some of those proteins would contaminate the viral preparations.  It was also likely that commercially available FVRCP vaccines contained those proteins.

From the American Journal of Veterinary Research (2004):

“Because the CRFK cell line is derived from a feline kidney tissue preparation, administration of FVRCP vaccines to cats could induce antibodies that also bind to feline renal tissues.” ¹⁶

In other words, cats receiving the FVRCP vaccine might develop autoimmune kidney disease as a result.

Apparently, this possibility deterred no one.  The vaccine was never re-formulated to eliminate the likelihood of contamination with CRFK cell proteins.  Nor does it appear that regulators ever seriously consider pulling it from the market.

Meanwhile, pet owners are continually assured that this vaccine is safe and effective.

So, to recap, it has been known for decades that the universally recommended and widely administered vaccine for feline distemper likely contains cell proteins with the potential to cause CKD in cats.  While no one knows exactly how common CKD is because the necessary studies have not been published, scientists have recognized for many years that this disease is prevalent in cats and that the numbers are on the rise.     

In light of these indisputable facts, pet owners would be forgiven for assuming that any possible connection between vaccination and kidney disease has been thoroughly explored and, since the distemper vaccine is still universally recommended, debunked.

Pet owners who assume this would be mistaken.

Ominous Signs

A study conducted by the Royal Veterinary College in London and published in 2016 in the Journal of Veterinary Internal Medicine attempted to identify risk factors for the development of CKD in cats.¹⁷ The researchers recruited 148 healthy cats over the age of nine, of which 86 had never been vaccinated. The rest of the cats had received either some or all of the recommended vaccines. 

The researchers tracked the health status of each of the cats over a period of several years.  They also administered a detailed questionnaire to the owners.  

At the conclusion of the study, the authors identified “frequent or annual vaccination and moderate and severe dental disease” as the leading risk factors for the development of CKD in geriatric cats.¹⁸

The study was small. The results appear to have been swept under the rug and duly ignored by the field of veterinary medicine.

Yet, these results should not have been surprising.  More than a decade earlier, a group of researchers from Colorado State University had sought to determine whether CRFK cell proteins could induce an antibody response to feline kidney cell lysates, which would signal the potential for the distemper vaccine to cause autoimmune kidney disease in cats.  They published their findings in 2005 in American Journal of Veterinary Research.¹⁹

The researchers exposed eight kittens to four doses of the distemper vaccine over a 50-week period.  Another six kittens received 11 inoculations of CRFK cell lysate over the same period, designed to approximate half the amount of CRFK cell protein that a cat would receive over its lifetime if it were vaccinated yearly against distemper. 

Six of the eight kittens in the first group developed antibodies to the CRFK cell protein, and five of the eight in that group developed antibodies to components of their own kidney cells.  In the second group, all six kittens developed antibodies to both the CRFK cell protein and to components of their own kidney cells.   

From the study:

“Parenteral [by injection] administration of vaccines containing viruses likely grown on CRFK cells induced antibodies against CRFK cell and FRC [feline kidney cell] lysates in cats….”

The authors noted that none of the kittens had developed kidney disease by the end of the 56-week study.  However, two of the 14 cats showed “mild interstitial inflammatory infiltrates comprised of lymphocytes, plasma cells, macrophages, and rare eosinophils.”    

This was hardly reassuring.

But the story does not end there.

The researchers housed eight of the 14 kittens together for the next year and fed them the same diet, then gave them another boost of CRFK cell lysate and biopsied their kidneys two weeks later.   This time, three of the eight kittens had evidence of interstitial nephritis, which is a common lesion in kidney failure. 

The authors wrote:

“We believe the most likely explanation for the detection of mild to moderate interstitial nephritis in three of the cats in the current study was an immune-mediated reaction against the CRFK lysates administered 2 weeks prior to biopsy. If this assumption is true, our failure to see significant numbers of inflammatory cells in biopsies obtained 6 weeks post-booster [in the first study] may have related to timing of the biopsy.” ²⁰

They also noted the possibility that inflammation following CRFK administration does not appear right away but can manifest over time.  Unfortunately, the researchers did not test the kittens for markers of kidney disease prior to administering the CRFK cell lysate boost.  Therefore, they could not tell us whether those inflammatory markers had appeared before or after the boost.

Regardless, the sample size for both studies was too small to predict what would happen to all cats with similar exposure. In addition, it is well-established that autoimmune disease from vaccination can take multiple years to manifest.  The fact that most of the kittens in the first study had developed antibodies to components of their own kidneys at the one-year mark, and three of eight kittens in the second study were already suffering from kidney disease at the two-year mark, did not bode well.

The authors noted that longer studies involving more cats were needed.  Yet, it appears that neither they nor any other researchers – in the U.S. or anywhere in the western world – has ever conducted such a study.  Why not?   Could it be that the field of veterinary medicine decided it didn’t want to know whether its universally recommended FVRCP vaccine was causing a terrible disease in cats?

For further clues, we must look to the East.  There again, the published data are scarce.  However, a study out of Thailand in 2021, from the Journal of Veterinary Science, attempted to expand upon this earlier work.  The researchers explored links between the frequency of FVRCP vaccination and the prevalence of antibodies that bind to kidney tissues. A total of 156 serum samples were collected from 69 unvaccinated and 87 FVRCP-vaccinated cats between 4 months and 16 years of age.   

The researchers found no direct link between the frequency of FVRCP vaccination and the prevalence of antibodies to kidney tissues.  They noted that nearly half the vaccinated cats in their study had no antibodies to the FVRCP vaccine.  They also reported that, surprisingly, time since last vaccination was not predictive of the presence of antibodies to FVRCP.  This finding contradicted earlier research, which purported to show a direct correlation between time since last vaccination and the presence of FVRCP antibodies. It suggests that cats differ in the strength of their immune response to this vaccine.

Nevertheless, the researchers found that having antibodies to FVRCP was, in fact, positively correlated with the presence of antibodies to kidney tissues.

They wrote:

“The odds ratio results showed that the association of finding antibodies that bind to kidney tissues in cats with antibody to FVRCP antigen was 2.8 times higher than in those without it…”

 They concluded:

“Thus, a feline vaccination schedule should be considered carefully, as over-vaccination might increase the risk of inducing the production of antibodies that bind to kidney tissues. Post-vaccination serology [titer tests, which measure the level of viral-specific antibodies found in the blood] should be used as a guide in deciding the need for repeated vaccination in order to avoid adverse reactions and prevent the risk of vaccine-induced autoimmune disease.” ²¹

These scientists were not the first to recommend routine titer testing.  A 2018 study published in the Journal of Feline Medicine and Surgery found no benefit to re-vaccinating healthy adult cats that already possessed an adequate level of antibodies to distemper. The authors advised against the practice.²²  

Unfortunately, if past is prologue, these studies will be ignored by most vets. Indeed, there is no indication of a shift in the field of veterinary medicine toward routine titer testing before deciding whether to boost cats with FVRCP vaccine.

The Third Rail

A longer investigation modeled on the Colorado State studies would be illuminating but would take years to complete.  While commencing such a study certainly should be a priority, cats and those who love them cannot afford to wait for those results. We need answers now.

A much faster way to answer the critical question of whether the distemper vaccine is a likely cause of CKD in cats would be via a large study comparing the prevalence of CKD in vaccinated vs. unvaccinated cats.   

One predictable argument against such a study will be that it’s simply not possible, because the vast majority of older cats in the U.S. – those most at risk for CKD – have received at least one dose of FVRCP at some point in their lives. 

This is a common tactic employed by those who don’t really want anyone looking under the vaccine hood.  For example, while claiming that the vaccine-autism link has been thoroughly “debunked,” government and industry groups have successfully blocked – for three decades now and counting – prevalence studies of autism, ADHD, and a multitude of other serious health and developmental disorders in vaccinated vs. unvaccinated children.²³ They do so, in part, by arguing that such studies cannot be done because there simply aren’t enough unvaccinated children to make up a sizeable unvaxxed control group.  (In the next breath, these same people argue that epidemics of measles and polio are just around the corner because of all the ignorant parents who no longer vaccinate their children. Go figure.) 

Granted, most kittens that start out in a shelter are likely to have been jabbed with FVRCP – not once but multiple times.  However, not all kittens are adopted from shelters. 

In addition, just as some parents are now foregoing one or more vaccines on the childhood immunization schedule, some pet owners, like me, have decided to forego one or more of the non-mandated vaccines on the pet schedule.  I currently have a seven-year-old male cat that was ten weeks olds when I adopted him from another family (not a shelter).  He has received zero doses of FVRCP.  How difficult would it be to find a few thousand more cats like him living in homes across America, and compare them to FVRCP-vaccinated cats for markers of kidney disease, while controlling for other possible contributing factors, including age, breed, diet, brand of cat litter, dental health, and weight? 

Those who don’t want to know the results of such a study should not be permitted to continue hiding the truth from the rest of us. 

Instead of a large study comparing vaccinated and unvaccinated cats, researchers in the U.S. feed us concocted studies like this one, published in 2014 in the Journal of the American Veterinarian Medicine Association.  

Researchers recruited cats nationwide from the Banfield Pet Hospital system. They compared 1,230 heavily vaccinated cats that had a clinical diagnosis of CKD to 1,230 heavily vaccinated cats that did not yet have the markers for CKD and found no significant difference in the rate of distemper vaccination in each group.  Thus, the authors concluded, the distemper vaccine does not cause CKD.²⁴

This is like saying, “We compared a group of people with lung disease who smoke heavily to a group of people who do not yet have lung disease but who also smoke heavily. Since both groups smoke heavily, cigarette-smoking does not cause lung disease.”

It is illogical on its face.

Neither Safe nor Effective?

The field of veterinary medicine clearly lacks the data to back its claim that the feline distemper vaccine is safe.

But is it effective? As previously noted, the vaccine is credited with dramatically reducing the rate of feline distemper in cats.  This may be true.  However, I was unable to find any published studies in the U.S. that either support or refute that claim.

What I did find were numerous studies that called into question the vaccine’s ability to consistently provoke an adequate immune response in kittens, which, as previously noted, is the age group most vulnerable to serious illness from distemper.

Kittens are born with maternally derived antibodies (MDA). Those antibodies protect the kitten from disease when they’re born but gradually fade. The period between the disappearance of protection from MDA and the ability to produce antibodies (and thus, protection) from vaccination is commonly referred to as the “critical phase” or “immunological gap.”²⁵ Researchers have found that even very low titers of MDA to distemper, while not generally protective of kittens, can interfere with the kitten’s ability to produce antibodies following vaccination. 

The majority of kittens in one study displayed significant titers of MDA at 12 weeks of age, which is up to eight weeks after the recommended first dose of FVRCP is administered to shelter kittens in the U.S.  In some kittens, MDA were still detected at 20 weeks.²⁶ This is beyond the age at which many kittens receive their final dose of FVRCP until adulthood. 

It should not be surprising, therefore, that those who have studied the effectiveness of the FVRCP vaccine in kittens report disappointing results.  A 2001 study published in The Journal of Feline Medicine and Surgery reported that 39 percent of kittens had no antibody response at the age of 15 weeks after three doses of FVRCP.²⁷ A 2012 study published in BMC Veterinary Research found that, despite triple vaccination – with the final dose administered at 16 weeks – 36.7 percent of kittens did not develop vaccinal antibodies.²⁸  

The authors concluded:

“In the given situation it is recommended to quantify antibodies against FPV [distemper] in the serum [blood plasma] of the queen or kittens before primary vaccination of kittens. The beginning of primary vaccination should be delayed until MDA titers have declined. Unprotected kittens that have been identified serologically should be revaccinated.”²⁹

Once again, this advice has been ignored.  The American Association of Feline Practitioners does not recommend testing for MDA titers in kittens prior to vaccination.³⁰ No doubt it is easier to simply to start jabbing kittens at a very young age and then hope for the best.  It is also more profitable for vets and pharmaceutical companies. Given that the FVRCP vaccine has not been proven safe, that philosophy is particularly troubling. 

Willow’s Legacy

Setting aside the question of effectiveness, until scientists can answer definitively whether the FVRCP vaccine causes chronic kidney disease in cats, I consider this vaccine a non-starter.   My own belief is that if we are going to intervene in nature on behalf of the animal kingdom, we had better be confident that we are not doing more harm than good.  Since the necessary studies have yet to be conducted, we have no way of knowing whether the vaccine for feline distemper is causing a much bigger problem than it’s solving.  

While I no longer allow any of my cats to receive this vaccine, I do take other steps to protect them.  I keep them indoors for starters. In addition, although I am involved in animal rescue, I do not bring rescued cats or kittens of unknown health status into my home.

However, when it comes right down to it, if I am forced to choose for any cat between the possibility of either seven days of acute illness, primarily during kittenhood, with a significant risk of death, or up to several years of chronic illness in adulthood, followed by certain death, I will choose the former.  Many people, no doubt, will disagree with me.  That’s fine. We can agree to disagree.

Tell me what you think in Comments Section below the references.

Up Next:  Feline Rabies

Then: Canine Rabies

1. Is it safe to vaccinate your pet? (substack.com)

2. ptpmcrender.fcgi (europepmc.org)

3. ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease - Andrew H Sparkes, Sarah Caney, Serge Chalhoub, Jonathan Elliott, Natalie Finch, Isuru Gajanayake, Catherine Langston, Hervé P Lefebvre, Joanna White, Jessica Quimby, 2016 (sagepub.com)

4. Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses - C. A. Brown, J. Elliott, C. W. Schmiedt, S. A. Brown, 2016 (sagepub.com)

5. Investigation of the induction of antibodies against Crandell-Rees feline kidney cell lysates and feline renal cell lysates after parenteral administration of vaccines against feline viral rhinotracheitis, calicivirus, and panleukopenia in cats - PubMed (nih.gov)

6. Longevity and mortality of cats attending primary care veterinary practices in England - Dan G O’Neill, David B Church, Paul D McGreevy, Peter C Thomson, David C Brodbelt, 2015 (sagepub.com)

7. Egenvall A, Nodtvedt A, Haggstrom J, et al. Mortality of life-insured Swedish cats during 1999–2006: age, breed, sex, and diagnosis. J Vet Intern Med. 2009; 23(6):1175–1183

8. The prevalence and classification of chronic kidney disease in cats randomly selected within four age groups and in cats recruited for degenerative joint disease studies - PMC (nih.gov)

9. Feline Panleukopenia - Generalized Conditions - Merck Veterinary Manual (merckvetmanual.com)

10. Distemper in Cats - Signs, Causes, Diagnosis, Treatment, Recovery, Management, Cost (wagwalking.com)

11. Vaccination against Feline Panleukopenia: implications from a field study in kittens | BMC Veterinary Research | Full Text (biomedcentral.com)

12. Vaccination against Feline Panleukopenia: implications from a field study in kittens - PMC (nih.gov)

13. Feline panleukopenia | American Veterinary Medical Association (avma.org)

14. djs_jaaha_56_5_COVER.indd

15. Vaccines for Cats: We Need to Stop Overvaccinating (catinfo.org)

16. Investigation of the induction of antibodies against Crandell-Rees feline kidney cell lysates and feline renal cell lysates after parenteral administration of vaccines against feline viral rhinotracheitis, calicivirus, and panleukopenia in cats - PubMed (nih.gov)

17. Risk Factors for Development of Chronic Kidney Disease in Cats (wiley.com)

18. Risk Factors for Development of Chronic Kidney Disease in Cats (wiley.com)

19. Investigation of the induction of antibodies against Crandell-Rees feline kidney cell lysates and feline renal cell lysates after parenteral administration of vaccines against feline viral rhinotracheitis, calicivirus, and panleukopenia in cats - PubMed (nih.gov)

20. doi:10.1016/j.jfms.2006.03.003 (catinfo.org

21. jvs-22-e38.pdf (nih.gov)

22. Antibody response to feline panleukopenia virus vaccination in healthy adult cats (core.ac.uk)

23. Summary | The Childhood Immunization Schedule and Safety: Stakeholder Concerns, Scientific Evidence, and Future Studies |The National Academies Press

24. Risk factors associated with the development of chronic kidney disease in cats evaluated at primary care veterinary hospitals in: Journal of the American Veterinary Medical Association Volume 244 Issue 3 () (avma.org)

25. Vaccination against Feline Panleukopenia: implications from a field study in kittens - PMC (nih.gov)

26. Vaccination against Feline Panleukopenia: implications from a field study in kittens - PMC (nih.gov)

27. A Field Trial to Assess the Effect of Vaccination against Feline Herpesvirus, Feline Calicivirus and Feline Panleucopenia Virus in 6-Week-Old Kittens (sagepub.com)

28. Vaccination against Feline Panleukopenia: implications from a field study in kittens - PMC (nih.gov)

29. Vaccination against Feline Panleukopenia: implications from a field study in kittens - PMC (nih.gov)

30. djs_jaaha_56_5_COVER.indd