Duration Of Immunity Research Articles

Long-term immunity induced by SPBN GASGAS in orally vaccinated dogs is non-inferior to inactivated rabies vaccines

In a long-term immunogenicity study (1100 days post vaccination) in local Thai dogs the immune response of the oral rabies vaccine SPBN GASGAS was compared to those elicited by a commercial inactivated vaccine using immunobridging. Based on the detection of rabies virus binding (rVBA) and rabies virus neutralizing antibodies (rVNA) as measured by ELISA and Rapid Fluorescent Focus Inhibition Test (RFFIT) the long-term immune response in dogs vaccinated orally with the SPBNA GASGAS strain of rabies vaccine in a bait was non-inferior to a conventional inactivated rabies vaccine. The outcome of this study supports extending the originally claimed duration of immunity (DOI) of SPBN GASGAS after oral vaccination for dogs from 6 to 30 months.

Vaccination and Antibody Testing in Cats.

Vaccines protect cats from serious diseases by inducing antibodies and cellular immune responses. Primary vaccinations and boosters are given according to vaccination guidelines provided by industry and veterinary organizations, based on minimal duration of immunity (DOI). For certain diseases, particularly feline panleukopenia, antibody titres correlate with protection. For feline calicivirus and feline herpesvirus, a similar correlation is absent, or less clear. In this review, the European Advisory Board on Cat Diseases (ABCD) presents current knowledge and expert opinion on the use of antibody testing in different situations. Antibody testing can be performed either in diagnostic laboratories, or in veterinary practice using point of care (POC) tests, and can be applied for several purposes, such as to provide evidence that a successful immune response was induced following vaccination. In adult cats, antibody test results can inform the appropriate re-vaccination interval. In shelters, antibody testing can support the control of FPV outbreaks by identifying potentially unprotected cats. Antibody testing has also been proposed to support decisions on optimal vaccination schedules for the individual kitten. However, such testing is still expensive and it is considered impractical to monitor the decline of maternally derived antibodies.

Evaluation of dog vaccination schemes against rabies in Kinshasa, Democratic Republic of the Congo

The traditional rabies control strategy based on annual mass vaccination of dogs appears to be costly and cumbersome. Given the existence of different risk zones for rabies transmission, the present study aimed at proposing risk-based vaccination schemes by considering canine population dynamics as well as vaccine efficacy and duration of immunity (DOI). The capital of the Democratic Republic of the Congo (RDC), Kinshasa, was chosen as study site. The turnover rate of dogs was used to assess their population dynamics in two low-roaming (<25 % of dogs are roaming) and in two high-roaming zones (>75 % of dogs are roaming). The sero-conversion rate was assessed in response to primo-vaccination in three age groups: 24 puppies (≤3months), 37 juveniles (4–12 months) and 22 adult dogs. The DOI was evaluated serologically by revaccinating dogs previously vaccinated since 1–2 years (n = 31), 2–3 years (n = 12) or 3–7.5 years (n = 4). Rapid Fluorescent Focus Inhibition Test was used to quantify antibodies. These data were used to implement vaccination outcome models.The turnover rate was twice as high in high-roaming zones (36 %) as that in lowroaming zones (17 %). Irrespective of roaming level, 75 % of dogs were less than 3 years old. The vaccine was equally effective in puppies (96 %), juvenile (97 %) and adult dogs (100 %, p = 0.24). The vaccine was effective in 93 % (11/12) of puppies without pre-vaccinal protective titers (≥0.5 IU/mL). The anamnestic response was strong within 5–8 days upon the booster vaccination, in 96 % (45/47) of dogs reported vaccinated 1–7.5 years before. This suggests that the vaccine provided a long-term protection (≥3 years) which is likely to occur in 75 % of dogs in Kinshasa.Hypothesizing a vaccination stop, the vaccination outcome model allowed to estimate the time point after which vaccination coverage would drop below 40 % in function of dog population turnover rate. The systematic vaccination of puppies as well as annual vaccination of dogs aged between 3 and 15 months or annual vaccination of all unvaccinated dogs aged more than 3 months of age appeared as valuable alternative to systematic annual mass vaccination.In conclusion, this study developed a vaccination outcome model pointing out the impact of dog population dynamics and of effective duration of immunity. It appears as a promising tool for designing cost-effective rabies vaccination campaigns

One Dose of a Novel Vaccine Containing Two Genotypes of Porcine Circovirus (PCV2a and PCV2b) and Mycoplasma hyopneumoniae Conferred a Duration of Immunity of 23 Weeks.

Porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhyo) are important swine pathogens for which vaccination is a key control strategy. Three separate studies were performed to evaluate the duration of immunity (DOI) conferred by a novel vaccine combining PCV2a/PCV2b and Mhyo into a ready-to-use formulation. In each study, three-week-old naïve piglets were vaccinated (Day 0) and challenged 23-weeks later (Day 159) with either PCV2a, PCV2b or Mhyo. Pigs were euthanized three-to-four-weeks post-challenge. Vaccinated pigs had significantly lower PCV2 viremia from Day 168 until Day 175 (PCV2a study) or until euthanasia (PCV2b study), respectively. Fecal shedding was significantly lower for PCV2a-challenged from Day 171 until Day 178, and for PCV2b-challenged from Day 172 until euthanasia. In the PCV2a challenge study, there were no differences among vaccinates and controls in terms of percent of pigs positive for PCV2 immunohistochemistry, histiocytic replacement, or lymphoid depletion. However, significant differences for immunohistochemistry and histiocytic replacement, not lymphoid depletion, were observed among vaccinates and controls following PCV2b challenge. Vaccination supposed a significant reduction in the mean percentage of Mhyo-like lesions in the lung. Percentages of lung tissues positive for Mhyo via immunohistochemistry were 49.3% and 67.1% for vaccinated and control groups, respectively. One dose of the novel PCV2a/PCV2b/Mhyo vaccine conferred robust protection against challenge 23-weeks later for all three fractions.

Immune duration of a recombinant PRRSV vaccine expressing E2 of CSFV

Classical swine fever virus (CSFV) and Porcine reproductive and respiratory syndrome virus (PRRSV) are both important pathogens which seriously harm the economic swine industry worldwide. We have previously demonstrated that rPRRSV-E2 is a promising live, virus-vectored vaccine that provides 100% protection against highly pathogenic PRRSV (HP-PRRSV) and CSFV. Here, we evaluated the duration of immunity (DOI) of the vaccine strain, rPRRSV-E2. Vaccine or cell culture medium was administered to piglets at 4 weeks of age. All immunized piglets developed high levels of antibodies, which could maintain for up to 23 weeks, against PRRSV and CSFV. All immunized pigs were well protected from the challenge of HP-PRRSV or CSFV at 20 weeks and 24 weeks post vaccination. The vaccine protection rate was still 100% at 24 weeks after immunization. The immune efficacy results showed that the immune duration of rPRRSV-E2 could be up to 5 months.

Gilt Vaccination with a Mixed Administration of a PRRS MLV and a PPV1 Subunit Vaccine Protects against Heterologous PRRSV1 Infection and Prevents Detrimental Effects on Piglet Performance.

The efficacy of the combined administration of a porcine reproductive and respiratory syndrome (PRRS) modified live virus (MLV) vaccine and a porcine parvovirus 1 (PPV1) subunit vaccine in gilts was addressed in two experiments. Experiment A aimed to establish a 4-week onset of immunity (OOI). Gilts were randomly distributed in three treatment groups: non-vaccinated control animals (group 1), animals vaccinated with the combined vaccine (group 2), and a third group that consisted of animals vaccinated with the PRRS MLV vaccine alone (group 3). Four weeks after the first vaccination, gilts were challenged with a heterologous PRRS virus 1 (PRRSV1) and euthanized three weeks after. Besides this, experiment B pursued a 17-week duration of immunity (DOI). In this case, gilts were distributed in the same treatment groups, but for the third group, which consisted of non-vaccinated, non-challenged animals were used instead. For the DOI assessment, gilts were artificially inseminated 4 weeks after the first vaccination, challenged at day 90 of gestation, and followed up, together with their offspring, until day 20 post-farrowing. Serology and viremia post-challenge were determined in gilts from both experiments, while farrowing and piglet performance were only evaluated in experiment B. Overall, the combined vaccine helped to protect gilts from viremia post-challenge and, consequently, to prevent PRRS clinical symptoms and diminish the proportion of piglets infected congenitally or early in life. The combined vaccine also elicited a significant improvement in piglet survival rate and growth performance until weaning. The present results reveal efficacy and lack of interference of the mixed use of the tested vaccines against PRRSV1 infection, with at least 4-week OOI and 17-week DOI.

Duration of immunity against heterologous porcine parvovirus 1 challenge in gilts immunized with a novel subunit vaccine based on the viral protein 2

BackgroundPorcine parvovirus 1 (PPV1) is widespread in commercial pig farms worldwide and has a significant impact to the swine industry. Long-lasting immunity achieved by means of vaccination is the main tool to prevent PPV1 infection and its associated clinical signs. Here we evaluated the duration of immunity (DOI) conferred by a novel subunit vaccine based on the viral protein (VP) 2 of PPV1, named ReproCyc® ParvoFLEX. The DOI was assessed at 6 months post-vaccination following the standard vaccination scheme (phase I) or after re-vaccination (phase II) with a single injection administered 24 weeks after the basic vaccination scheme. A total of 46, five to six-month-old gilts, free of PPV1 and porcine reproductive and respiratory syndrome virus (PRRSV), were randomly assigned to 6 groups (three in each phase): the negative control groups were inoculated with sodium chloride (NaCl), the vaccinated groups were immunized with the PPV1 subunit vaccine and the strict controls were neither treated nor challenged. Subsequently, the negative control and vaccinated groups from each phase were challenged with a heterologous PPV1 strain. Infection of fetuses was the primary outcome parameter for efficacy, though other supportive parameters were PPV1 viremia and serological status of the gilts and the condition of their fetuses (i.e. normal, autolytic, or mummified).ResultsAll gilts vaccinated against PPV1 tested seropositive at challenge and viremia after challenge was detectable only in the non-vaccinated animals. In this regard, fetuses positive to PPV1 by PCR were only found in litters from non-vaccinated sows.ConclusionsThese results point out that the immunity developed by the PPV1 subunit vaccine is effective in terms of preventing viremia, transplacental infection of fetuses and fetal death caused by PPV1 infection. ReproCyc® ParvoFLEX was demonstrated to protect fetuses against heterologous PPV1 challenge with a DOI of 6 months after vaccination.

Duration of immunity for an inactivated Mycoplasma hyorhinis vaccine in pigs

Mycoplasma hyorhinis (Mhr) is a pathogen of pigs causing polyserositis and polyarthritis. The most susceptible population are nursery pigs of approximately 7 weeks of age, although we have shown that clinical signs can persist into finishing aged animals after a late-nursery infection. We have previously demonstrated the efficacy of a novel inactivated Mhr vaccine for the reduction of lameness and polyserositis in caesarian-derived colostrum-deprived (CDCD) pigs vaccinated at 3 weeks and challenged with Mhr at 6 weeks of age. Here we evaluated the duration of immunity (DOI) of the same vaccine. Vaccine or placebo was administered to CDCD pigs at 3 weeks of age. Pigs were challenged with Mhr at either 10 weeks of age (=7 week DOI) or 13 weeks of age (=10 week DOI). In the 7 week DOI, vaccination provided significant reductions in lameness (p = 0.0018), arthritis (p = 0.0002), and pericarditis (p = 0.0312) versus the placebo control. In the 10 week DOI, a significant reduction in arthritis (p = 0.0320) was observed in the vaccine group as compared to the placebo group. Both vaccine groups showed a significant increase (p < 0.0001) in the post-challenge average daily gain (ADG), gaining 0.2 kg/day more than their respective placebo groups.

Assessing the immunogenicity of an inactivated monovalent vaccine in the endangered African wild dog (Lycaon pictus)

Captive held African wild dogs (Lycaon pictus) were vaccinated with a commercially available inactivated canine parvovirus (CPV) vaccine licensed for use in domestic dogs. Serological responses were recorded by testing for viral antibodies with the haemagglutination inhibition test (HAI) following a vaccination schedule involving two initial inoculations a month apart and an annual booster. Vaccines were delivered by hand injection or remotely (i.e. by dart). All naïve dogs vaccinated with Parvac® did seroconvert as determined by canine antibody titres ≥ 1:80 in one or more samples collected after inoculation. Duration of immunity (DOI) within the first year persisted for approximately 98 days only. To enable greater immunological protection revaccination should occur more frequently than once in a calendar year. No significant differences in the seroprotection rate were observed when comparing route of administration.

Recommendations on vaccination for Asian small animal practitioners: a report of the WSAVA Vaccination Guidelines Group.

EXECUTIVE SUMMARYIn 2012 and 2013, the World Small Animal Veterinary Association (WSAVA) Vaccination Guidelines Group (VGG) undertook fact‐finding visits to several Asian countries, with a view to developing advice for small companion animal practitioners in Asia related to the administration of vaccines to dogs and cats. The VGG met with numerous first opinion practitioners, small animal association leaders, academic veterinarians, government regulators and industry representatives and gathered further information from a survey of almost 700 veterinarians in India, China, Japan and Thailand. Although there were substantial differences in the nature and magnitude of the challenges faced by veterinarians in each country, and also differences in the resources available to meet those challenges, overall, the VGG identified insufficient undergraduate and postgraduate training in small companion animal microbiology, immunology and vaccinology. In most of the countries, there has been little academic research into small animal infectious diseases. This, coupled with insufficient laboratory diagnostic support, has limited the growth of knowledge concerning the prevalence and circulating strains of key infectious agents in most of the countries visited.Asian practitioners continue to recognise clinical infections that are now considered uncommon or rare in western countries. In particular, canine rabies virus infection poses a continuing threat to animal and human health in this region. Both nationally manufactured and international dog and cat vaccines are variably available in the Asian countries, but the product ranges are small and dominated by multi‐component vaccines with a licensed duration of immunity (DOI) of only 1 year, or no description of DOI. Asian practitioners are largely unaware of current global trends in small animal vaccinology or of the WSAVA vaccination guidelines. Consequently, most practitioners continue to deliver annual revaccination with both core and non‐core vaccines to adult animals, with little understanding that “herd immunity” is more important than frequent revaccination of individual animals within the population.In this paper, the VGG presents the findings of this project and makes key recommendations for the Asian countries. The VGG recommends that (1) Asian veterinary schools review and increase as needed the amount of instruction in small animal vaccinology within their undergraduate curriculum and increase the availability of pertinent postgraduate education for practitioners; (2) national small animal veterinary associations, industry veterinarians and academic experts work together to improve the scientific evidence base concerning small animal infectious diseases and vaccination in their countries; (3) national small animal veterinary associations take leadership in providing advice to practitioners based on improved local knowledge and global vaccination guidelines; (4) licensing authorities use this enhanced evidence base to inform and support the registration of improved vaccine product ranges for use in their countries, ideally with DOI for core vaccines similar or equal to those of equivalent products available in western countries (i.e. 3 or 4 years).The VGG also endorses the efforts made by Asian governments, non‐governmental organisations and veterinary practitioners in working towards the goal of global elimination of canine rabies virus infection. In this paper, the VGG offers both a current pragmatic and future aspirational approach to small animal vaccination in Asia. As part of this project, the VGG delivered continuing education to over 800 Asian practitioners at seven events in four countries. Accompanying this document is a list of 80 frequently asked questions (with answers) that arose during these discussions. The VGG believes that this information will be of particular value to Asian veterinarians as they move towards implementing global trends in small companion animal vaccinology.

Canine vaccination — a review for veterinary nurses

ABSTRACT:Vaccines used routinely for canine vaccination include modified live vaccines (MLVs) and killed vaccines. MLVs have higher immunogenicity than killed vaccines meaning that they are more successful at eliciting an immune response. Studies into the duration of immunity (DOI) of MLVs have helped introduce the extended revaccination interval of three years and many vaccine manufacturers have now relicensed their products for such use. Although suspected adverse reactions (SARs) to vaccination are rare, extended revaccination intervals should help reduce the number seen in practice. It is important to be aware of the possible reactions and to ensure these are reported appropriately. Vaccine failure is rare but may arise owing to poor response on the part of the individual, the presence of maternally derived antibodies (MDA) and environmental factors, such as inappropriate vaccine storage. The Vaccination Guidelines Group (VGG) recommendations cover the issue of maternally derived antibodies (MDA), extended revaccination intervals and the use of serology to determine whether a booster is needed.

Duration of immunity induced by companion animal vaccines

Concerns about possible adverse effects from annual vaccination have prompted the reanalysis of vaccine protocols for cats and dogs. In the last decade, several veterinary advisory groups have published protocols that recommend extended revaccination intervals for certain 'core' vaccines. In addition, practicing veterinarians have been asked to consider vaccination as an individualized medical procedure, based on an analysis of risks and benefits for each vaccine in an individual animal. The calls for extended revaccination intervals prompted considerable debate in USA and internationally. Areas of concern include the amount of evidence to support prolonged immunity from various vaccines, the risk of poor responses in individual animals and the possible effects on population immunity. This review examines how the duration of immunity (DOI) to a vaccine is established in animals and humans. It reviews factors that can affect the DOI in an individual animal, including the types of immune defenses stimulated by the pathogen, and the vaccine, host factors such as age and the level of exposure to the pathogen. In addition, it examines DOI studies that were published for canine and feline core vaccines.

COMPILED BY THE VACCINATION GUIDELINES GROUP (VGG) OF THE WORLD SMALL ANIMAL VETERINARY ASSOCIATION (WSAVA)

The WSAVA Vaccination Guidelines Group (VGG) was convened in order to develop guidelines for the vaccination of dogs and cats that have global application. The first version of these guidelines was published in 2007 and they were updated in 2010. The present document provides a further updated and expanded version of these international guidelines for the vaccination of small companion animals and indicates the scientific evidence base on which the recommendations are made. The VGG recognises that the keeping of pet small animals is subject to considerable variation in practice and associated economics throughout the world and that vaccination recommendations that might apply to a developed country may not be appropriate for a developing country. These guidelines are not a mandatory edict, but rather should be used by national associations and individual veterinary practices to develop vaccination schedules relevant locally. However, the VGG strongly recommends that wherever possible ALL dogs and cats receive the benefit of vaccination. This not only protects the individual animal, but provides optimum ‘herd immunity’ that minimises the likelihood of infectious disease outbreaks. With this background in mind, the VGG has defined core vaccines as those which ALL dogs and cats, regardless of circumstances or geographical location, should receive. Core vaccines protect animals from severe, life-threatening diseases that have global distribution. Core vaccines for dogs are those that protect against canine distemper virus (CDV), canine adenovirus (CAV) and the variants of canine parvovirus type 2 (CPV-2). Core vaccines for cats are those that protect against feline parvovirus (FPV), feline calicivirus (FCV) and feline herpesvirus-1 (FHV-1). In areas of the world where rabies virus infection is endemic, vaccination against this agent should be considered core for both species, even if there is no legal requirement for routine vaccination. The VGG recognizes that maternally-derived antibody (MDA) interferes with the efficacy of most current core vaccines administered to pups and kittens in early life. Because the level of MDA varies among litters, the VGG recommends administration of multiple core vaccine doses to pups and kittens, with the final dose given at 16 weeks or older and followed by a booster at 6- or 12-months of age. In cultural or financial situations where a pet animal may only be permitted the benefit of a single vaccination, that vaccination should be with core vaccines at 16 weeks of age or older. The VGG supports the use of simple in-practice tests for determination of seroconversion to the core vaccine components (CDV, CAV, CPV-2 and FPV) following vaccination, for determination of seroprotection in adult dogs and for management of infectious disease outbreaks in shelters. Vaccines should not be given needlessly. Core vaccines should not be given any more frequently than every three years after the 6- or 12-month booster injection following the puppy/kitten series, because the duration of immunity (DOI) is many years and may be up to the lifetime of the pet. The VGG has defined non-core vaccines as those that are required by only those animals whose geographical location, local environment or lifestyle places them at risk of contracting specific infections. The VGG has also classified some vaccines as not recommended (where there is insufficient scientific evidence to justify their use) and has not considered a number of minority products which have restricted geographical availability or application. The VGG strongly supports the concept of regular (usually annual) health checks which removes the emphasis from, and client expectation of, annual revaccination. The annual health check may still encompass administration of selected non-core vaccines which should be administered annually, as the DOI for these products is generally 1 year. The VGG has considered the use of vaccines in animal shelters, again recognising the particular circumstances of such establishments and the financial constraints under which they sometimes operate. The VGG minimum shelter guidelines are simple: that all dogs and cats entering such an establishment should be vaccinated before, or at the time of entry, with core vaccines. Where finances permit, repeated core vaccines should be administered as per the schedules defined in the guidelines and non-core vaccines against respiratory disease may be included. The VGG recognizes the importance of adverse reaction reporting schemes, but understands that these are variably developed in different countries. Wherever possible, veterinarians should be actively encouraged to report all possible adverse events to the manufacturer and/or regulatory authority to expand the knowledge base that drives development of improved vaccine safety. These fundamental concepts proposed by the VGG may be encapsulated in the following statement: We should aim to vaccinate every animal with core vaccines. Non-core vaccines should be given no more frequently than is deemed necessary.

Duration of immunity (DOI) and booster vaccination—dealing with the issue at practice level in the UK

The presentation offers a UK veterinary practitioners viewpoint on issues of DOI and booster vaccination with reference to both dog and cat vaccines. The current use of vaccines and issues surrounding their use are discussed, including motivations for and against vaccinating in a climate of reduced fear of disease, and increased suspicion of vaccines. Attitudes to extended DOI and routine booster vaccinations are explored, and specific disease and prevention issues concerning leptospirosis in particular are presented. The strategy and tactics of implementation of extended DOI vaccines at general practice level are discussed based on the author's own experiences, and thoughts offered on how vaccine manufacturers might support the process at local and national levels, as well as communicating a positive message for continued routine vaccination of dogs and cats, and the advantages that extended DOI offers.

Duration of immunity (DOI)—The regulatory issues

This paper discusses the efficacy of cat and dog vaccines, with respect to duration of immunity and regulatory issues. The European Union (EU) regulatory requirements are described: briefly, efficacy claims, which include duration of immunity, have to be specific for the product and supported by controlled laboratory and field trials. As a result, the duration of immunity shown has typically been a minimum, because of the cost and welfare implications of keeping animals for long periods of time in isolation. In contrast, in the US, duration of immunity has not traditionally been required for each individual product, only for rabies vaccines and some other vaccines for which no other products are available. The consequence of this is that in the US, various scientific authorities have produced guidelines appropriate for individual diseases. Undoubtedly this will continue, although the regulatory authorities also appear to be moving towards a position where lack of information may be indicated on the product label, and studies are required to support extended duration of immunity claims. The advantages and disadvantages of laboratory challenge studies versus field trials are discussed, and the use of alternatives such as surrogate markers of protection. The approaches used for small animal vaccines are compared to those used, for example, in human medicine. The main issue for small animals is that unlike in some other species, the aim generally is to maximise protection in the individual, rather than induce protection at the population level. The drawbacks of the present EU system are summarised, and the ways in which the situation is currently being approached and improved are presented.

Serological testing—An alternative to boosters?

The issue of the duration of immunity, particularly for the modified live viral components of veterinary vaccines, has been a significant part of the recent vaccination debate. One manufacturer has increased the recommended booster interval for these components to 3 years give name and another now states ‘up to 4 years’ immunity. There remain many unanswered questions regarding this duration of immunity (DOI). Studies suitable for data sheet claims are time consuming and costly and can only be performed in laboratory dogs under tightly controlled conditions. Evidence from rabies serology testing in the UK shows that the response of individual animals to routine vaccination is highly variable. Much of the published field evidence on the persistence of antibody titres originates from North America, where vaccination strategies and reservoir species differ from Europe. Quantifying the effect of exposure to field virus on the maintenance of immunity in these studies is impossible, and little is known of the circulation of virus in unvaccinated dogs and wild mammals throughout Europe. If owners or vets are concerned about revaccination one option is to assess the need for each booster by performing a blood test. There is some published evidence of the relationship between antibody titres and protective immunity, and tests are available to measure responses to individual viral components of the routine canine and feline vaccines. It must be remembered that most commercial tests to assess immunity only measure antibodies, which are only one aspect of the immune response to vaccination. It is therefore possible that animals without or with low antibody titres are in fact protected. Serological tests are an option if owners are unwilling to have their animal boostered without evidence that it is needed. However, the cost of these tests is likely to exceed that of booster vaccination for the foreseeable future.