Chapter 28 Principles of Vaccination Flashcards
What is the primary goal of vaccination in equine medicine?
To control and prevent infectious diseases.
Where can guidelines for vaccinating horses in North America be found?
On the American Association of Equine Practitioners (AAEP) website.
What is the difference between vaccine efficacy and vaccine effectiveness?
Vaccine efficacy refers to the reduction in disease incidence in a vaccinated group under optimal conditions, while vaccine effectiveness refers to the vaccine’s performance in real-world settings.
How is vaccine efficacy usually evaluated in equine medicine?
Through experimental infections of research horses rather than randomized controlled trials (RCTs).
What are the limitations of vaccine efficacy studies?
Their results may not accurately reflect vaccine performance under field conditions.
What is the principal advantage of vaccine effectiveness studies?
They provide data from real-world settings, which can be more reflective of actual vaccine performance.
What is the main limitation of vaccine effectiveness studies?
The presence of many biases that can influence the results.
Why is vaccine efficacy generally expected to be higher than vaccine effectiveness?
Because efficacy studies are conducted under strict, controlled conditions.
How is vaccine efficacy calculated?
Using the formula: (incidence in unvaccinated - incidence in vaccinated) / incidence in unvaccinated * 100.
What formula is used to calculate vaccine efficacy using a risk ratio?
Efficacy = (1 - RR) * 100.
How can vaccine effectiveness be evaluated?
Using either cohort or case-control study designs.
What is the rationale for evaluating vaccine efficacy and effectiveness?
Evidence of efficacy is required for licensure, and evaluating effectiveness is important for developing better vaccines and informing cost-effectiveness.
What are core vaccines according to the AAEP?
Vaccines against tetanus, Eastern and Western equine encephalitis, rabies, and West Nile virus.
What is herd immunity?
A phenomenon where vaccination of a significant portion of the population provides protection to the whole herd, including unvaccinated individuals.
Why is herd immunity not applicable to diseases like West Nile virus encephalomyelitis?
Because the infection is vector-borne and horses are dead-end hosts.
What are the four types of vaccine-associated adverse events defined by the CDC?
Vaccine-induced events, vaccine-potentiated events, programmatic errors, and coincidental events.
What are vaccine-induced adverse events?
Events that would not have occurred in the absence of vaccination, attributable to the vaccine’s properties and the individual’s response.
What are vaccine-potentiated adverse events?
Events that might have occurred anyway but are precipitated by vaccination.
What are programmatic errors in vaccination?
Adverse events due to technical errors in vaccine storage, preparation, handling, or administration.
What are coincidental events in vaccination?
Events that happen by chance or due to an underlying illness, not causally associated with vaccination.
Why is it challenging to maintain proper vaccine storage conditions for ambulatory veterinarians?
Both excessive heat and freezing can alter vaccines, reducing efficacy and potentially increasing adverse reactions.
What systems does the CDC support for vaccine safety data monitoring?
Vaccine Adverse Events Reporting System (VAERS), Vaccine Safety Datalink (VSD), and Clinical Immunization Safety Assessment (CISA).
How does the USDA Center for Veterinary Biologics (CVB) administer adverse event reporting for equine vaccines?
Through a voluntary reporting program, though the data collected are sparse and under-representative.
What information should veterinarians record to assist with reporting adverse events?
The vaccine manufacturer’s batch and lot numbers, and the site of injection.
What is the recommendation for booster vaccine administration regarding injection sites?
Booster vaccines should not be administered at the same site as the initial vaccination.
What are localized reactions following vaccination usually attributable to?
Preservatives or adjuvants included in the vaccine, rather than the agent-specific components.
Why might combination vaccines have more adverse events than individual vaccines?
Because they include multiple antigens and preservatives, which may increase the likelihood of reactions.
What is the impact of maternal antibody interference on foal vaccination?
Maternal antibodies may interfere with the immunogenicity of vaccines, leading to reduced antibody production.
Why is vaccination often delayed until foals are six months old?
To avoid maternal antibody interference and ensure a stronger immune response.
What is a potential downside of delaying foal vaccination until six months of age?
An ill-defined sub-population of foals may remain vulnerable to infection during a window when maternal antibodies have waned.
Why are inactivated vaccines generally preferred during pregnancy?
They are considered safer for the fetus compared to live-organism vaccines.
What are the considerations for vaccinating mares during pregnancy?
Vaccination can boost colostral antibodies for foals, but there is a risk of local or systemic reactions and premature delivery.
What is the recommendation for vaccinating mares against equine viral arteritis (EVA)?
Vaccination should not be administered during the last 60 days of pregnancy or the first six weeks of a foal’s life.
What are the core vaccines recommended by the AAEP?
Vaccines against tetanus toxoid, Eastern and Western equine encephalitis virus, rabies virus, and West Nile virus.
Why might risk-based vaccination schedules vary even within the same barn?
Because the risk of exposure differs based on geographical, environmental, and individual characteristics of the horses.
What factors should veterinarians consider when designing vaccine protocols?
Geographical region, season, horse’s age, activity level, and specific risks of exposure to infectious diseases.
What is the rationale for vaccinating horses more frequently than once annually in regions with active mosquitoes?
To maintain protective antibody levels throughout the mosquito-active season.
What is a key gap in knowledge regarding vaccination during pregnancy?
There is limited evidence on the long-term health effects of repeated vaccination of mares during late gestation.
What are the potential benefits of vaccinating foals against Rhodococcus equi or equine herpesvirus-1?
Protection primarily through cell-mediated immunity, as humoral responses may be poor markers of protective immunity.
What is the impact of non-steroidal anti-inflammatory drugs (NSAIDs) on immune responses to vaccination in horses?
It remains unclear, though some evidence suggests short-term use of low to moderate doses should not impact vaccinal responses.
What is the recommended vaccination practice for neonatal foals and geriatric horses?
Special consideration should be given due to their increased risk of infectious disease and potentially less responsive immune systems.
What are the key knowledge gaps in equine vaccinology?
Vaccination during pregnancy, maternal antibody interference, the number of vaccines or antigens, and the impact of anti-inflammatory administration for horses with vaccine reactions.
Why is it important to follow current literature and AAEP guidelines for vaccination protocols?
Because recommendations may become outdated as new information and vaccine technologies emerge.
How can vaccine effectiveness be influenced by storage and administration practices?
Improper storage or dilution can reduce the effectiveness of the vaccine.
What is the significance of calculating vaccine effectiveness using odds ratio (OR) from a case-control study?
It helps evaluate vaccine performance in real-world settings where disease cases and controls are representative of the population.
What is the impact of herd immunity on the perception of vaccine effectiveness?
High vaccine coverage can lead to most cases occurring among vaccinated horses, creating a paradoxical perception that the vaccine is not effective.
What is the role of epidemiological studies in identifying vaccine-associated adverse effects?
They help clarify associations and identify rare adverse reactions that may not be apparent in smaller pre-licensure studies.
How does the CDC classify vaccine-associated adverse events by severity?
From mild events like local reactions to severe events like anaphylactic reactions.
