Canine Vaccination–A Survey of Owner Attitudes and Adherence to Vaccination Protocols

1. Introduction

Vaccination has been hailed as one of the “greatest contributions to global health of any human intervention”, with its success in controlling and eradicating diseases (Greenwood, 2014). Many diseases have been eradicated through the use of vaccination, with smallpox being the most famous (Davenport et al., 2018), but also huge reductions in potentially fatal companion animal diseases, such as canine distemper and parvovirus have also been seen through successful vaccination programs (Truyen, 2006). Successful rabies vaccination programs of wildlife have been implemented in various parts of the world, for example in northern Europe where use of an oral bait vaccine has led to the eradication of rabies in this region (Muller et al., 2015; Pastoret and Brochier, 1996).

However, in 2019 the World Health Organization (WHO) named ‘vaccine hesitancy’ as one of its top ten threats to global health (Geoghegan et al., 2020). Vaccine hesitancy is defined as “the reluctance or refusal to vaccinate despite the availability of vaccines” (Akbar, 2019). With the apparent control of many serious diseases, thanks largely to mass vaccination, has come public complacency and a rise in an ‘anti-vaccine movement’ (Salmon et al., 2015). This was evident during the recent SARS Covid-19 outbreak, although the reasons behind this are not well understood (Dror et al., 2020; Machingaidze, and Wiysonge, 2021; Trojano and Nardi, 2021). Subsequently, there has been an increase in the number of people declining vaccination for themselves and their children, potentially due to fear of vaccine-associated adverse effects (VAAEs) and the belief that vaccines may cause more harm than good (Salmon et al, 2015). The infamously incorrect link between the measles, mumps and rubella (MMR) vaccine and autism (Eggertson, 2010) has furthered this effect, and this resulted in tens of thousands of parents not giving their children the MMR vaccine which in turn led to outbreaks of diseases that were once considered virtually ‘eliminated’ (Hussain et al., 2018).

The veterinary sector has recently seen a ‘record decline’ in the number of pets being vaccinated in the UK, with the number of dogs receiving primary vaccinations falling 18% over the past three years, and only a third receiving regular booster vaccinations (PAW report, 2019). This reduction might reflect the same hesitancy seen for human vaccination and an increased fear regarding the safety and efficacy of pet vaccinations. In recent years, vaccination protocols for dogs have been the subject of great debate (Day, 2006) and frequent changes. Canine core vaccinations are defined by the World Small Animal Veterinary Association (WSAVA) as those vaccines which “All dogs and cats, regardless of circumstances or geographical location, should receive” and include canine parvovirus (CPV), canine distemper virus (CDV), and canine adenovirus (CAV 1 & 2) (Day et al., 2016). In the UK, leptospirosis has also been added to these core vaccines, due to its zoonotic potential (BSAVA, 2015), and in the USA, rabies has been added and is required by law in many states (Welborn et al., 2011).

Until recently, canine vaccines were licensed with a minimum duration of immunity (DOI) of only one year, and so vets typically vaccinated dogs with every vaccine annually (Day et al., 2016). However, there were increasingly frequent reports of mild to very serious VAAEs, and so, in response to public and media pressure, the World Small Animal Veterinary Association (WSAVA) formed the Vaccination Guidelines Group (VGG) to produce vaccination guidelines based on evidence-based research with global applicability (Day et al., 2016). The WSAVA recommended that for adult dogs, core vaccines should be administered no more often than triennially (although this depends on the vaccine used), and most canine vaccines now reflect this three-year recommendation (Day, 2017). However, this is a minimum DOI, whereas for most core vaccines, serological and challenge studies have demonstrated protection for considerably longer (Schultz et al., 2010). Evidence also suggests that environmental boosting through natural exposure can help keep immunity levels high for dogs (Welborn et al., 2011).

The WSAVA guidelines also recommend the use of triennial serological titer testing for core vaccines CPV, CDV & CAV 1 & 2 to assess seropositivity and the requirement for core vaccine boosters (Day et al., 2016, 2017). However, titer tests cannot be used for leptospirosis or rabies, therefore, dogs whose geography or lifestyle places them at risk of exposure to leptospirosis or who regularly travel, must still receive annual re-vaccination to leptospirosis to stay protected and triennial vaccination to rabies to stay within legal requirements (Day, 2017).

In 2019, the People’s Dispensary for Sick Animals (PDSA) raised concern in its Animal Wellbeing (PAW) Report, that since 2016, there has been a steep decline in primary puppy vaccination uptake leaving them at significant risk of contracting viral and bacterial diseases, “owing to the incomplete ability of their immature immune system” (Cardillo et al., 2020). In its survey, the PDSA found 72% of dogs received primary vaccines, which is a marked reduction from 88% in 2016, and also showed a reduction in dogs which were regularly receiving booster vaccinations (78% down from 82%) (PAW report, 2019). Although there are no data that state what percentage of dogs require each vaccine to create herd immunity for control or eradication of each core disease, it is reported that a coverage of 75% is required (Day et al., 2016). The PDSA reported that the main reasons for the decline in pet vaccination (including cats and rabbits) were that it is too expensive (17%), not necessary (16%) or their pet finds going to the vets stressful (13%) (PAW report, 2019).

There are limited studies investigating potential reasons why there has been a drop in vaccine uptake. Recently German researchers reported that a wide number of different factors were associated with owner compliance to vaccination of dogs within German national vaccination guidelines including kennel visits, and veterinarian advice (Eschle et al, 2020). Prior to this, there were two studies investigating vaccination rates in cats. These aimed at understanding factors involved in cat owners’ decisions to vaccinate and their knowledge regarding feline vaccinations (Habacher et al., 2010; Gehrig et al, 2019). Thus, the aim of this study was to develop a greater understanding of the factors involved in dog owners’ opinions towards vaccination of their dogs internationally, and to explore whether the decline in vaccination is complemented by an increase in alternative methods such as titer testing.

2. Materials and Methods

2.1. Ethical Note

This study was approved by the University of Lincoln ethics committee (reference number 2217). Data were obtained in compliance with general data protection regulation (GDPR) requirements and owner consent was collected at the start of each survey with an opt-in system. All data collected were anonymous, and no personal contact data was requested.

2.2. Dog Owner Recruitment

A questionnaire was generated using Qualtrics software (Qualtrics Provo, UT, USA, 2020) to recruit dog owners within the UK and internationally, via social media platforms Facebook and Twitter. Multiple dog focused groups were selected to share the questionnaire and generate a snowballing effect where participants further shared the survey on various personal pages or dog groups for a three-month period between March 10^th and June 10^th, 2020.

2.3. Survey Design

The questionnaire consisted of 35 questions split into four sections (see appendix B). The first section requested demographic information regarding the owner. The second section requested information about a single dog that they own, avoiding complications regarding answering for multiple dogs. The third section requested information regarding the dog’s history of vaccination and the owner’s attitudes towards vaccinations including alternative methods. The last section requested information on their dog’s other health care measures, such as diet, in part to deter the respondent from a focus and potential bias towards vaccinations. All items were closed, requiring selection from multiple choice or binary yes/no answers, although some also included an optional ‘other’ free-text box for elaboration. In addition, UK respondents were presented with a map of the UK to allow them to indicate which region they lived in.

2.4. Statistical Analysis

After collation of simple summary descriptions, the binary logistic regression analysis function in Minitab 19® Statistical Software (State College, PA: Minitab, Inc 2019) was used to model the data. A stepwise backwards model selection process using all available potential factors, was performed using the Akaike information criterion using a significance level of 0.05.

The aim was to answer the following research questions:

• RQ1. What factors significantly predict whether someone is less likely to have vaccinated in the past 12 months?
• RQ2. What factors significantly predict whether someone who has not vaccinated in the past 12 months, uses titer testing?

Analysis for the second question was performed on a reduced data set, only including respondents who had selected ‘no’ for the question ‘vaccinated in the past 12 months. Model assumptions were checked, most notably multicollinearity and outliers. Outliers were determined by analysis of the residuals/fit. A goodness-of-fit test was done to test model fit indicating a good fit for both models Q1 (Hosmer-Lemeshow: Chi-Square=2.74, df=8, p-value=0.950); Q2 (Hosmer-Lemeshow: Chi-Square =10.54, df=8, p-value=0.229).

The statistical metrics p-values, chi-square, odds ratio (OR) and confidence intervals were used for the interpretation. Reference categories were selected by using the response options that had the highest proportion of respondents. An OR > 1 showed an increased expected probability and an OR <1 showed a decreased expected probability in relation to their respective reference categories.

3. Results

3.1. Survey Response

A total of 2,993 questionnaires were completed. 385 were removed as incomplete surveys, 14 removed as participants were under 18 years of age, 7 for duplicate responses and 2 for non-consent to take part. This left, 2,585 responses for initial analysis.

There was a distribution across age groups, with the 18-39 and the 40-59 age group each making up around 40% of the participants respectively (Table S1), although the female respondents were highly overrepresented, making up 95% of participants. Different levels of education were all well represented within the participant cohort, with 39% having a degree, 18% having a higher degree, 10% with A or AS levels and 11% with vocational awards. The remaining participants had various other educational qualifications (Table S1). Employment status varied with 46% working full time, 13% employed part time, and 16% self-employed. The remainder were students or unemployed for various reasons (25%). Salaries were equally variable, with 26% having an income of under £20,000, and 23% earning between £21 and £40 000. The remaining 28% earned over £41,000 and 23% did not want to reveal their salary data (Table S1).

Although the study is heavily UK-based, with 49.71% of participants, there were 114 participants from the USA and Canada, as well as others from Europe (19) and Australia and New Zealand (n=21) (Figure S1). Within the UK, there was a fair spread across most parts of the UK, but only a small number of respondents (n = 5) from Northern Ireland. In terms of education, 56.8% (1470) respondents had a university education, with 1003 (68.2%) having an undergraduate degree, and 467 having a higher degree.

Dog age was also varied, although most participants owned dogs which were under three years old (38.95%), and this is the age where animals should be receiving early vaccinations and worming/ flea treatments as their immune system is still developing. A mix of pedigree and cross breed animals were included (Table S1). Owners had obtained their animals from a wide variety of different areas, with breeders (30.6%) and dog shelter adoption (33.6%) being the two most popular. Most animals had received some level of training, but most of this was self-taught (81%) but often in conjunction with other methods. 1.1% of animals were not registered with a veterinarian, 51% were uninsured, 21.9% were not neutered, and then 6.8% were not microchipped (table S1).

Of the dogs included in the study, 21% of the animals were not vaccinated (Table 1, Figure 2), 61.8% of animals were receiving yearly vaccination, and 2% were never vaccinated. Although the majority of people in the study did vaccinate their pets, there were still a wide variety of reasons given for non-vaccination; 17.9% of people claimed they did not vaccinate their pets over concern of adverse health effects on the animal, and 9.9% of animals felt that the vaccination was not required. Other less common reasons included cost (2.66%), stress to the animal when visiting the vets (2.2%) and a lack of contact with other dogs (2%) (Figure S2). Time to take the pet to the vets for the vaccination appeared not to be a big issue with the participants (0.8%) (Figure S2).

The reasons why people vaccinate their pets regularly are summarized in Table 2. The most common reason related to concern over the severity of the disease which the dog could catch, and the importance of protecting against it; 48.2% highlighted the importance of veterinary advice on their decision, and 15.7% had vaccination included within their plan with their vet. Pressure from third parties such as dog kennels or catteries to show proof of vaccination to allow their animals to stay.

Interestingly, 69% of the respondents to the questionnaire had heard about negative reactions to vaccination, with 16.4% of people claiming to have encountered them themselves (Table 2).

To further probe the details of the negative reactions which people had encountered or heard of with vaccines, the respondents were asked to name conditions and signs which they had heard could be linked to vaccination. The more common answers were allergies (37.5%), lethargy (33.4%), soreness at injection site (25.5%), seizures (28.4%), autoimmune problems (24.3%), lack of appetite (22.8%), diarrhea (21.2%), death (19.7%), nausea, (19.1%), fever (19.1%), and face or limb swelling (11%) as well as behavioral issues, including aggression and reactivity (6.7%), (Table 3). Autism was referred to by 3% of respondents. All the reported negative effects reported by participants are reported in Table 3.

Veterinarians were a common source of information for 83.7% of people, with personal research and internet also popular (42.5% and 18.8% respectively) (Figure S3). Other animal professionals such as behaviorists, breeders, trainers or rescues were an important source of information for 12% of respondents. Interestingly, 86 dog owners reported that they had never looked to seek any advice.

Other methods such as detox have been suggested instead of vaccination, and 20.4% of the respondents had heard of it, with 28.6% of these people having tried it.

For comparative purposes it is worth noting that flea treatments were used by 69.8% and worming treatments by 74.6% of participants, with 6.7% using unknown alternative methods for flea and worm treatments. 67.9% of participants had heard about negative effects to one or both of these treatments, and 16.7% claimed to have actually experienced these. These were not examined further in the survey though.

Along with vaccination, anti-flea and anthelminthic treatments are commonly used to protect animals from infestations and infections respectively. Therefore, it was assessed if those who do not vaccinate do not take other preventative control methods. Reasons for anthelminthic and flea treatments were very similar to those seen for vaccination uptake, with 51.1% occurring during a veterinary consultation, and 57.6% doing it out of concern for their pet’s health (Table S2). Interestingly, 55.4% were flea and worm treating to prevent infestation within the house, and that may be due to the biting behavior and general annoyance caused by fleas, or through knowledge of zoonotic risk of parasites (Table S2). But again, surprisingly, 12.8% of the participants did not treat their pets regularly (Table S2) although how this corresponds to the animals lifestyle is unknown.

Interestingly, there was a wide variety of different diets being used by the participants of this study to feed their pets, including dry and wet food. Raw food was used by a large percentage of people for their pets too (homemade- 15.2% and commercial- 22.8%) despite concerns regarding balanced diets and the risk of zoonotic infections (Table S2). Advice again was from veterinarians (52.8%), veterinary nutritionists (21.5%), or their own learned research (53.9%). 38.5% got their nutritional information from the internet which is unsurprising, and 28.5% got their information from their friends or fellow dog owners (Table S2). Again, professionals like behaviorists, groomers and breeders provided nutritional information for 15.7% of participants, and again, it may be pertinent to offer appropriate training to these professionals as part of their continued professional development (Table S2).

The most interesting factors associated with the response ‘vaccinated in the past 12 months’ were answering yes to ‘Lack of time to go to the vets’ (n = 20/2,585; OR 8.5; 95% confidence interval [CI] 1.9-37.7), answering no to ‘flea and worm regularly due to products being part of pet plan’ (n = 297/2,581; OR 7.3; 95% CI 2.3-22.5) due to their high association with a negative response to the target question (Table 4). Additionally, answering yes to ‘Vaccinate regularly due to requirement of third party-proof’ (n = 657/2,585; OR 0.3; 95% CI 0.2-0.5) due to its high association with a positive response to the target question.

3.2. Factors Predicting Whether an Owner Who Did Not Vaccinate in the Previous 12 Months, Uses Titer Testing

Based on the AIC model selection, multiple factors were associated with ‘titer test and vaccinate when required’ (Table 5 and Table 6). The most interesting of which are answering yes to ‘Education or work in vet or nutrition industry’ (n = 9/540; OR 8.5; 95% CI 1.3-53.9), answering yes to ‘feeding cold pressed/ air dried/ freeze-dried dog food’ (n = 66/540; OR 4.0; 95% CI 1.9-8.5) and answering yes to ‘advice received regarding nutrition from a nutritionist’ (n = 177/540; OR 3.6; 95% CI 2.2-6.2) due to their high association with a positive response to the target question. Note that the factor ‘Education or work in vet or nutrition industry’ was chosen to be included despite the small sample size noting this result may vary with a larger sample; of the responses six answered they titer test while three answered they did not titer test. Additionally, answering no to ‘heard of negative effects after vaccinating’ (n = 479/543; OR 0.1; 95% CI 0.03-0.5) due to its high association with a negative response to the target question.

4. Discussion

This study was designed to assess vaccination in pets, and why, or why not owners choose to treat their pets with the relevant vaccines and other treatments. The results showed that 79% of dogs in the study were vaccinated in the past 12 months. In comparison, a recent German study regarding dog vaccination compliance found that only 47% of dogs were vaccinated annually to recommended levels (including leptospirosis; Eschle et al., 2020); however, this research focused only on German dog owners, whereas the respondents of this current study were global but heavily biased to Europe and the USA.

Vaccination protocols may differ significantly between countries. Though World Small Animal Veterinary Association (WSAVA) guidelines are meant for international guidance, they acknowledge some countries may have differing non-core vaccination requirements depending on disease risk level and legal requirements. This study, for example, found there was a large difference between numbers of those who vaccinated in the previous year between the USA/ Canada (89%) and the UK (70%). In the UK, there are no legal obligations to vaccinate any dog (requirements exist only for international travel and for entry to kennels and some dog shows), whereas in the USA (where rabies is endemic) annual vaccination is legally required in many states, even for products licensed with a 3-year duration of immunity (DOI) (Day et al., 2016). The WSAVA guidelines, however, are not mandatory (Day et al., 2016), and there are still vet practices in the UK and abroad that do not follow these guidelines and still encourage core annual re-vaccination regardless of the vaccine used (Eschle et al., 2020). This could be due to adherence to traditional practice or fear of financial loss. Additionally, owners may be less willing to vaccinate within the UK due to the lack of severe zoonotic infections, due to the UK being rabies free, and the other viruses not causing any real known issues to human health (although noting that Leptospira is a zoonotic, but rare in the UK). Recent studies by Taylor et al., (2022) showed that around 50% of dogs had at least a single vaccine dose for protection against Leptospira given within the 12 months of the study, suggesting that half are missing out on protection against a potentially serious zoonotic disease.

This study found that owners were more likely to have vaccinated their dog in the past 12 months if required by a third party, such as a day care or putting their animal into a dog shelter. This is in line with previous studies who found a higher vaccination rate in dogs staying in boarding kennels where disease risk is often higher due to rapid turnover, and close contact with many animals from different backgrounds (Eschle et al, 2020). Mandatory vaccination has previously been seen in human governance. In the UK, the Vaccination Act of 1853 made it a legal requirement to vaccinate against smallpox, which ultimately led to its eradication (Amin et al., 2012). Some may call for a similar move in companion animal vaccination. However, increasing doubts about making childhood vaccinations mandatory and the consequential breakdown of trust between parents and health professionals (Elliman and Bedford, 2013) are also likely to appear with any attempt to impose mandatory vaccination regimes for pets. Indeed, vaccine hesitancy was seen in high levels in the SARS covid-19 outbreak of 2019-2022, although the reasons why this was the case are poorly understood and require more sympathetic research (Dror et al., 2020; Machingaidze, and Wiysonge , 2021; Trojano and Nardi, 2021).

Of particular interest was the mention of autism in dogs post vaccination, with 3.1% (80 people) having ‘heard that a dog had developed it.’ This is interesting given the rapid decrease in MMR vaccination due to concerns that it was linked to autism as suggested by Andrew Wakefield (now withdrawn). If this has made the jump into veterinary medicine, that could prove highly problematic for vaccine uptake. Although this has been mentioned by people in the past, there is no evidence of the existence of autism in dogs, nor what the clinical signs would be, but this aspect requires further research (Burton et al., manuscript in preparation).

Owner demographics such as having a lower income or living in areas of the UK that are less affluent had no statistical relevance to whether owners vaccinated in the previous year. This is not supported by previous studies which found that vaccination rates were higher in more affluent areas, and with those with higher education levels (Sánchez-Vizcaíno et al., 2018; PAW report, 2019). However, the reason for this difference could be due to how data was collected. The use of Facebook groups and voluntary sampling in this study may attract a skewed demographic, whereas the previously mentioned studies collected data from either veterinary electronic health records or through active sampling which could guarantee them better coverage of certain demographics. However, the UK is currently undergoing a cost-of-living crisis, and thus it is perceived that the level of pet vaccination and other pathogen control methods (anthelminthic and flea treatments) may decrease further, although this remains to be seen. There is a high number of respondents who had received significant education (degree level or higher), and this is likely to reflect that the study was done as part of a post graduate study.

No statistical relevance was discovered regarding the dog’s demographics. However, 28% of the dogs included were aged two years or less and 93% of these dogs were vaccinated in the previous 12 months. This follows previous findings that found younger dogs were more likely to be vaccinated (Eschle et al, 2020). This could be due to owners being more aware of the importance of initial puppy vaccinations for immunity, or alternatively, when they purchase a puppy it is commonly from a breeder who will likely (if they are reputable) to have had the puppy vaccinated. Owners of older dogs may assume that immunity is lifelong, and they may be correct as evidence shows that these dogs do hold immunity to core vaccines (CPV, CDV & CAV 1 & 2) for many years, sometimes the lifetime of the dog (Schultz et al., 2010). However, this could be due to environmental challenge, which constantly acts to boost the immune system for common viruses such as CPV.

A significant factor that influenced whether an owner chose not to vaccinate their dog in the previous 12 months, was that the owners stated they had a lack of time to go to the vets. This suggests that rather than an active political or personal decision to be ‘anti-vaccination’, for many it is simply a matter of convenience. Studies into why people do not attend their NHS medical heath checks within the UK show that one of the top reasons is having a lack of time or competing priorities (Harte et al., 2017). It seems plausible that this would also apply to attending a veterinary appointment outside of emergency situations, especially if the need for vaccination is perceived to be not required. If lack of time is a main concern to keep up to date with required vaccines, a way to make it easier and more convenient for them could be to increase availability of mobile vets who come to their home, or local area, to administer preventative health care. This would also be helpful for those owners who vaccinate less due to their dog being stressed by going to the vets, or those people with mobility or travelling issues. Implementation of mass rabies vaccination of pet dogs in Africa was conducted via mobile vets in an attempt to control the disease (Athingo et al., 2020) and this was thought to prove relatively successful. They found a critical need for the success of the program was public education via awareness campaigns featured in different media sources. Targeted education measures have been proven to increase vaccinations rates (Cory et al., 2019) and maybe worth an investment from local veterinary groups and or the Department for Environment, Food and Rural Affairs (DEFRA) to encourage more pet vaccine uptake.

This study also found that if people regularly flea treat and worm their dogs as part of a yearly health plan, then they were more likely to have vaccinated their dog in the previous 12 months. This suggests that if a dog’s health care measures are included in a pre-paid package, then owners would be more likely to vaccinate yearly. Pet health plans are a clever marketing idea, which can be useful to encourage dog owners to attend annual health checks. However, this appears to work well, as visiting a vet was a common reason why pet dogs were vaccinated. There is a concern that if owners see vaccination as the only reason for attending their vet annually, and they choose to not vaccinate, that vets will not see dogs frequently enough to recognize and treat other undiagnosed diseases (Day, 2017). It is important to stress to puppy owners the benefits of continued annual check-ups for other health care concerns beyond vaccination. Reminder cards in the post, or more conveniently a mobile phone app with notifications, could be a useful way of helping owners to remember when preventative health care is required for their dog.

In the PAW report, it was found that 28% of their surveyed dogs had not received initial puppy vaccinations. This study only found 2% that had never received vaccinations and the German research only 1% (Eschle et al, 2020). This could suggest that even those owners who vaccinate less than recommended have still acquired at least preliminary puppy vaccinations for their dogs and thus are not ‘anti-vaccination’ in mindset but instead possibly ‘anti-overvaccination’. Anti-overvaccination is different from what is commonly perceived within the ‘antivaccination’ community for humans, where vaccine hesitancy means some children are not vaccinated at all. Anti-overvaccination questions whether vaccinating annually or even triennially is safe or required. The WSAVA’s updated guidelines support using triennial serological testing in lieu of revaccination every three years (Day et al., 2016). Dogs who have responded to core vaccinations, not including leptospirosis, should have a protective immunity that can be maintained for many years (Day et al., 2016; Schultz, 2006). In this study, 13% of respondents stated that they use titer testing. Titer testing is a method that can be used to assess the level of antibodies circulating in a dog’s blood (NOAH, 2019). The presence of adequate serum antibody to declare a protective titer, can determine whether that dog requires a booster vaccine or not (Killey et al., 2017). Titers for vaccines for leptospirosis are limited because antibodies persist only for short periods (Day et al., 2016) and have been found to give only significant protective immunity for 12 months after vaccination (Klaasen et al., 2014). However, leptospirosis, in particular the new Lepto4 vaccine, is a controversial vaccine which has been linked with VAAE’s, including allergic events, immune-mediated disease, anaphylaxis and death (Day et al, 2016; Telegraph.co.uk, 2016). However, titer testing results may cost more, and results can take a few days to come back, and therefore people may prefer to vaccinate their pet rather than spend more on a titer test and have to visit a veterinary practice twice in quick succession. This way it also reduces the requirement for invasive procedures to draw blood for titer testing.

This study found that owners who had heard of negative effects after vaccinating were more likely to titer test if they had not vaccinated their dog in the previous 12 months. In total, 69% of owners stated they had heard of negative side effects due to vaccination, with 16% stating that they had personal experience of them from their dog. In this study, the top five adverse reactions that owners thought could relate to canine vaccination were: allergies (37%), lethargy (33%), seizure or convulsions (28%), soreness at the injection site (25%) and autoimmune problems (24%). Previous research on cats has shown that VAAEs negatively affect future vaccination decisions (Gehrig et al, 2019). However, some VAAEs, such as pain, swelling, and redness at the injection site are considered common (Kimmel, 2020), therefore it can be complicated to differentiate between acceptable VAAEs and those that question the safety of that vaccine. According to the Veterinary Medicines Directorate (VMD), in 2019 (the last year where full data is available pre covid), there were 3,578 adverse reaction reports in dogs, which include all drugs administered to dogs, including vaccinations (VMD, 2020).

A retrospective cohort study on the adverse events diagnosed within three days of vaccine administration in dogs states that VAAEs have some inherent risk factors and may be generally underreported (Moore et al., 2005). Although VAAEs are relatively infrequent in the population, there are certain concerning factors such as a significant increase of risk with number of vaccines administered per visit and small-breed dogs being at greater risk of a reaction (Moore et al, 2005). A large-scale survey conducted in Japan looked at adverse reactions after non-rabies vaccinations. They found a much higher rate of VAAEs than reported in the UK (0.093/10,000 vaccinated dogs) or USA (38.2/10,000 vaccinated dogs) (Miyaki et al, 2011). They also found a higher prevalence of VAAEs in certain small breeds suggesting a possible genetic predisposition but admitted that there may have been breed bias with the popularity of small breeds in Japan (Miyaki et al, 2011).

It was found that owners who had not vaccinated their dog in the previous 12 months were more likely to titer test, if they have worked or studied within the nutrition or vet industry. It seems plausible that owners who express an interest in relevant fields would be more aware of procedures such as titer testing as a recommended and evidence-based safe alternatives to vaccinating a dog more often than may be necessary (Day et al, 2016). It could be argued that, in future studies on vaccination levels, dogs that have been titer tested and proven to have protective immunity should be included in the vaccinated population rather than the unvaccinated population and therefore as contributing towards herd immunity of certain core canine diseases.

Owners who did not vaccinate in the previous 12 months were found to be more likely to titer test if they fed ‘healthier’ dog food or they sought canine diet advice from a nutritionist. These owners would appear to take extra time and effort to find healthier alternatives for their dogs and are willing to research, pay for professional advice and feed premium dog food products. However, general confusion can be created for dog owners looking for evidence-based information when researching via the internet and even for ‘experts’ in certain fields. Amongst professionals, there is disagreement over certain health movements for dogs. For example, whether raw food diets are dangerous (Schmidt et al., 2018; Davis, 2018) or the ‘gold standard diet for pets’ (Raw Feeding Veterinary Society, 2020). There are scientists that have criticized the rise of alternative pet medicine and diets, even linking these choices to the antivaccination movement itself (Chambers & Belshaw, 2018), although there is still much more research to be done in the area of raw food diets and vegan pet diets to assess their safety and benefit (or lack thereof) to pets. It is perhaps worth investigating training non veterinarian professionals to improve their ability to advise pet owners on areas associated with vaccination, anthelminthic and flea treatments to ensure gold standard treatments are initiated.

Overall, this study found vaccination rates to be higher than previous studies have found. There are limitations with this study as it was international, and vaccinating protocols vary from country to country. The information provided in the survey is susceptible to the recall bias of each owner. The internet and access to Facebook or Twitter was required in order to take part in the survey. In the past, this may have been a limitation but recent national statistics in the UK show that 93% of households have access to the internet (Prescott, 2019), while 66% of the UK own a Facebook page (Statista, 2015).

This survey was referred to as the ‘Dog Health Care’ survey to avoid bias from preconceptions on attitudes towards vaccination. Random dog groups were chosen, rather than targeting dog health groups, to avoid selection bias. However, due to the snowball effect of sharing the survey, it is unknown which Facebook pages or groups the survey was ultimately shared to. Due to the survey being shared on dog focused Facebook groups, owners with a strong interest in dogs and their care may have been more motivated to take part resulting in some bias. It has been found that social media sites such as Facebook can create polarized groups with echo chambers, where information with poor evidence goes unchallenged; there are many such sites regarding the vaccination debate (Schmidt et al., 2018). The internet can be a large source of misinformation, about topics such as vaccination. This is apparent during the coronavirus pandemic and the search for a vaccine. The WHO coined the term ‘infodemic’ to describe an “overabundance of information and the rapid spread of misleading or fabricated news, images, and videos. Like the virus, it is highly contagious and grows exponentially and plays a major role in complicating the COVID-19 pandemic response efforts” (WHO, 2020).

There were significantly more female participants than male, therefore there could also be a gender bias. It has been found women are more likely than men to seek health information online and twice as likely as men to seek material regarding the health of their child (Fox & Rainie, 2002). Dogs are treated and considered part of the family and hold a relationship often like that of a parent-child bond (Dotson and Hyatt, 2008). In modern society, maternal instincts have extended from children to pets, such as dogs (Prato-Previde et al, 2006), thus women particularly could be more likely to join Facebook groups dedicated to dogs and respond to a survey regarding their care.

This study has identified factors associated with the likelihood or not of vaccinating dogs within a 12-month period and further factors associated with determining whether someone who has not vaccinated their pet dog in the past 12 months, uses titer testing instead. However, with a low incidence of non-vaccination and a high incidence of annual vaccinations, there was no evidence to suggest in this study that dog owners are affected by the anti-vaccination movement identified as causing issues for human immunology and the fight to prevent, control and eradicate diseases. There does appear to be a rise in concern regarding over-vaccination in dogs which has been addressed by the WSAVA with updated guidelines for safer vaccination protocols and encouragement to use titer testing triennially. Rather than dog owners being considered ‘anti-vaccination,’ there may be a move towards owners becoming more informed and basing vaccination choices on this.

5. Conclusions

This study in the UK investigates issues with vaccine uptake, and suggests some factors which merit follow-on research. Further research in the area of canine vaccinations would be helpful to look at whether anti-vaccination attitudes are present, but this study found no evidence that dog owners are avoiding vaccination or hesitant to vaccinate their pets. There may be a lean towards following WSAVA guidelines and vaccinating less for core vaccines or titer testing. As vaccination rates were lowest in the UK, compared to other countries, represented in this study, it would also be interesting to explore internationally what vaccination protocols vet practices are following, as it may be that many still do not follow WSAVA guidelines.