Vaccination

What is the purpose of vaccination?

To form memory B and T cells, protect the individual, generate herd immunity, and provide safe and effective administration.

What is the difference between active and passive immunization?

Active: induces an adaptive immune response, long-lasting, can be re-stimulated, but has a delay in protection. Passive: provides immediate, short-lived protection, but can interfere with active immunity and cause hypersensitivity.

What are examples of passive immunity?

Artificial immune globulins, colostral antibodies.

What are examples of active immunity?

Artificial immunization (living or non-living vaccines), natural infection.

What are advantages of passive immunity?

Immediate protection, homologous transfer lasts longer.

What are disadvantages of passive immunity?

Interferes with active immunity, type III hypersensitivity, repeated doses can lead to IgE release and anaphylaxis.

What are advantages of active immunity?

Long-lasting, can be restimulated, induces adaptive immune response.

What is a disadvantage of active immunity?

Delay in onset of protection.

What is an ideal vaccine?

Cheap, stable, mass-producible, free of adverse effects, elicits strong immunity.

What are modified live vaccines (MLV)?

Culture-attenuated pathogens that are antigenic but avirulent.

What are advantages of MLVs?

Single-dose efficacy, induce strong CMI and humoral responses, not frozen.

What are disadvantages of MLVs?

May revert to virulence, may spread to unvaccinated animals, less stable, difficult to handle/store.

What are killed vaccines?

Inactivated vaccines processed exogenously that require adjuvants.

What are advantages of killed vaccines?

Safer for pregnant or immunodeficient animals, more stable.

What are disadvantages of killed vaccines?

Require multiple or high doses, higher risk of hypersensitivity, increased cost.

How are organisms in killed vaccines inactivated?

Formalin, alcohol/acetone, alkylating agents.

What are toxoids?

Inactivated bacterial toxins that stimulate long-lasting immunity.

What is an antitoxin?

Immunoglobulin raised against a toxin, provides artificial passive immunity for immediate, short-term protection.

What are bacterins?

Killed whole bacteria vaccines, more hypersensitivity reactions, poor duration of immunity.

How do live vaccines stimulate the immune system?

Act as endogenous antigens, replicate in host cells, stimulate Th1, Th2, CMI, and humoral responses.

What are disadvantages of live vaccines?

May revert to virulence, spread to other species, contamination risk, handling/storage difficulty.

What are recombinant vaccines?

Genetically engineered vaccines.

What is a Category 1 recombinant vaccine?

Gene cloning to synthesize antigen in non-pathogen; requires many adjuvants.

What is a Category 2 recombinant vaccine?

Genetically attenuated organism with virulence gene deleted; can revert to virulence.

What is a Category 3 recombinant vaccine?

Genes encoding antigen cloned directly into recombinant organisms.

What are DNA vaccines?

Plasmid injected into host cells to produce antigen, expressed on MHC I.

What is attenuation?

Weakened pathogen strain produced by passage in culture.

What is serosurveillance?

Measuring antibodies in a population to differentiate between vaccinated and infected animals.

What are adjuvants?

Substances added to vaccines to enhance protection.

What are depot adjuvants?

Provide slow release of antigen.

What are irritating adjuvants?

Cause macrophage granulomas or abscesses.

What are particulate adjuvants?

Make antigens readily phagocytosed.

What are immunostimulant adjuvants?

Promote cytokine production.

How is immunity transferred to the newborn?

Through colostrum rich in IgG; in birds via yolk (IgY) and egg white (IgA).

What is the risk of fetal infection from vaccines?

Modified live vaccines can cause fetal infection or tolerance due to antigen exposure in utero.

What are core vaccines?

Vaccines used to protect against diseases endemic to a region.

Why do young dogs and cats receive a series of vaccines between 8 and 16 weeks?

Because maternal antibody wanes variably; repeated doses ensure immunity is established despite interference.

What are possible causes of vaccine failure?

Incorrect administration, giving to already infected or passively protected animals, wrong strain/antigen, animal immunosuppression, biological variation, or inadequate vaccine.

What are possible risks of vaccination?

Fibrosarcoma, hypersensitivity, disease in immunocompromised, immunosuppression.

What are vaccine titers?

Measurements of antibody levels that may correlate with immunity.

What are limitations of vaccine titers?

Do not assess CMI or memory cells, not standardized.

What do high vaccine titers suggest?

Probably protection.

What do low vaccine titers suggest?

Do not necessarily indicate lack of protection.

What is the importance of vaccine storage and handling?

Improper storage/handling can kill live vaccines or reduce effectiveness.

How is vaccine safety and effectiveness determined?

Through controlled trials and measuring outcomes like morbidity/mortality reduction.

How do you calculate preventable fraction?

(control deaths/sick - vaccinated deaths/sick) ÷ (control deaths/sick) × 100.

What are some possible adverse events due to vaccination?

Hypersensitivity, fibrosarcoma, immunosuppression, disease in compromised animals.