Lecture 6 - Vaccines I

How is the best vaccination achieved for acute, non-lethal infections?

Immunity from natural infection (not always ideal)

What is the goal of a vaccine? How long does it take for protection to occur?

-Goal is to prevent clinical signs and transmission

-Takes 2 weeks

What is vaccine efficacy?

Ability to prevent or reduce clinical signs while still inducing an antibody response

What is vaccine safety?

No undesirable side effects or vaccine reversion

What are the components of a disease control program from most important/effective to least?

1. Hygiene and sanitation (biosecurity, vector control, disinfection)

2. Quarantine (at least 3 weeks)

3. Vaccination

What are the ideal properties of a vaccine?

-Stable (no cold-chain requirement)

-No virus shedding

-Provide sterilizing immunity

-Deliver protection in one dose

-Contain a DIVA marker and companion diagnostic test

-Cost effective

-Resistant to pre-existing blocking antibody

-Safe

What did the Plowright vaccine protect against? Why was it so effective?

-Rinderpest vaccination

-Live-attenuated and delivered life-long immunity in one dose

-Stable with no reversion to virulence

-Highly protective

-No vaccine virus shedding

-Temperature stable

What are inactivated virus vaccine? What type of immunity does it stimulate?

-Virus is inactivated and an adjuvant is added

-Generally only stimulates humoral immunity (T_H2)

What are the important considerations of an inactivated virus vaccine?

-Generally safer but more likely to cause allergic reaction

-Requires boosters

-Slower onset of protective immunity

-May not stimulate strong or long-lasting immunity

-Susceptible to blocking by pre-existing antibody

-Incomplete inactivation of virus can lead to disease outbreaks

What is the function of an adjuvant?

Tells the body to mount an immune response

Why is timing so important when giving an inactivated virus vaccine?

Maternally derived antibodies (MDA) protects neonates but can also block successful vaccination of young animals

What is a modified live virus vaccine (MLV)? What type of immunity does it stimulate? What is an advantage?

-Virus is weakened or altered

-Stimulates T_H1 and T_H2 immunity

-Usually only requires one dose

What are important considerations when using a modified live vaccine?

-May produce moderate to severe clinical disease

-Possible reversion to virulence

-Physically unstable

-May produce persistent infection

-May require cold chain and/or on site preparation

-Possibility of contamination of cell line with other agents

What are subunit vaccines?

Purified and/or concentrated viral proteins (mechanical/chemical treatment or recombinant techniques)

What are the advantages to a subunit vaccine?

-Increased potency (better for immune protection_

-Can differentiate infected from vaccinated animals (DIVA markers)

What is a DIVA (Differentiating Infected from Vaccinated Animals) marker?

Allows for distinction between animals that have been vaccinated and those that are naturally infected with a disease