vaccines and vaccinations Flashcards
vaccine
a preparation of an immunogenic material used to induce immunity against pathogenic organisms (product you use)
vaccination
intentional administration of a harmless or less harmful form of a pathogen to induce specific immune response that protects the individual against later exposure to the pathogen
the way we take advantage of the body’s normal immune response to PROTECT animals fr. disease
vaccinated or not?
- consider costs/risks and benefits (economic decision)
What is main objective of vaccination?
- passive transfer of immunity => vaccinated breeder, progeny come w/ immunity
- active immunity => own immune system protects us
- immunity against disease & infection
- sterile immunity: elimination of pathogen before it replicates
- vaccination in face of infection/disease
non-infectious application of vaccination
- vaccines to induce self tolerance => expose to different levels of antigen and person gets used to it
- anti-cancer vaccines (Marek’s in poultry)
- vaccines against drug addiction
- contraceptive vaccines
the ideal vaccine
- safe: vaccine itself must not cause illness or death
- protective: must protect against illness resulting fr. exposure to live pathogen
- gives sustained protection: must last several years
- induces neutralizing antibody: some pathogens like poliovirus infect cells that cannot be replaced
- neutralizing antibody essential to prevent infection of such cells
- induces protective T cells: some pathogens, particularly intracellular, are more effectively dealt w/ by cell mediated responses
- practical considerations: low cost per dose, biological stability, ease of administration, few side-effects
immunity
2 types
- innate: non-specific, already present at birth
- acquired: resistance that individual develops after exposure (like vaccine)
- initial cell mediated response to antigen
- macrophages, neutrophils, NK cells
- T & B cells: acquired (generate memory)
- cell mediated response (T cells)
- humoral or antibody response from B cells
Primary and secondary
primary immunogenic stimulus
- latent period -> exponential phase (IGM) -> primary response where first antibody shows up (at steady state)
- IgM turns into IgG as it declines
secondary immunogenic stimulus
- faster time in response
- IgM -> IgG (secondary response is memory response that causes high IgG and longer in time)
what do we look on vaccines?
- safety
- do limited harm to recipient
- stimulate protective immune response against pathogens
- maximize return on investment (food animal)
what is in a vaccine vial
- micro-organisms: live, attenutated, inactivated or parts of microorganisms)
- certain parts of bacteria
- adjuvant, immunological agent that increases the antigenic response (mostly in inactivated vaccines)
- something put into vaccine to stimulate the antigenic response
- preservatives, formaldehyde, gentamycin, dyes etc.
vaccines available in poultry medicine
live virus transformed into modifided live virus, inactivated virus, or recombinant product
modified live virus: isolate from wildtype, let it grow, do it many times => when put in chicken, can have secondary effects
- will cause full immune response => innate, adapted, great immune response and memory
inactivated virus: get virus and mix it w/ formalin which kills virus and fixes product (keep structure of protein in good shape) which allows virus to generate good immune response
- problem: doesn’t replicate so not constantly stimulating immune response
- need adjuvants to stimulate more than one
recombinant: inserting gene of interest into vector that will generate protein that induces in immunity that’s protected
- generates antibodies in host that’s protective against disease
live virus -> purified subunits
isoalte portions of virus => can use that as vaccine
strategies explored as vaccines (CoV)
inactivated: sinovac => approved abroad
mRNA: moderna and pfitzer/BioNTech => emergency use approved
virus vectored: J&J => emergency use approved
virus-like particles: Novavax => waiting for ER use approval
- largest amount of vaccine candidates in clinical and pre-clinical stages
- aim for 95% protection
types of vaccines
side note: primary infection can get infected by bacteria
ex: clear -> green snot
live or modified live vaccines (MLV)
- live attenuated product
- replicate in the animal and shed to others
- stimulate cell mediated and humoral immunity (complete immunity)
- long lasting immunity
-vaccinated population => if not, have rolling infection
killed vaccines
- inactivated
- don’t replicate in animals
- stimulates humoral immunity (Ab’s), requires priming (w/ live vx)
- short lived systemic immunity (1-2 yrs)
- stimulate primarily B-cells Ab but no SMI
- safer, no reversion to virulence
- good for producing antibodies
-good first response = better 2nd response (at least 2 doses)- may require revaccination throughout animal’s life = jey to immunologic memory
- adjuvants: stimulate greater response
- maybe cause adverse reactions
- injection site granulomas
- pathogen isn’t causing flu, the agulents are => can cause severe secondary effect
recombinant vaccines
- a live vector carries gene (fr. pathogen) encoding a protein of immunogenic interest
- long lived immunity thanks to live vector b/c vector constantly replicating => generates lots of antibodies
- generates immunity to the gene of interest (GOI) and vector
- make sure there is no previous immunity to the vector (neutralizes the vaccine)
- very safe
- require liquid nitrogen storage
safety of the vaccines
MLV
- can induce disease (reversion to virulence) => b/c didn’t vaccinate whole population, virus jumps to other chickens and is getting adopted again
- may cause abortion in mammals
- requires refrigeration to keep it alive
killed vaccine
- safer, no reversion to virulence
- adjuvant often irritating (granuloma formation)
- difficult to apply (parenteral)
- expensive: the encapsulation, not mRNA
recombinants
- safe, no reversion to virulence
- applied in ovo, IM or SC (poultry)
- expensive
routes of administration
- parenteral: intramuscular (IM), subcutaneous (SC), intradermal (ID)
- mucosal: oral, nasal, rectal, ocular, and vaginal (spray, drinking water, gel)
- epidermal and transcutaneous delivery
- in-ovo immunization (chickens)
- fetal immunization (mammals)
occular vaccination
in chickens, usually for respiratory diseases
subcutaneous vacination
base of neck, legs, Marek’s in poultry
intramuscular vaccination
mostly inactivated vaccines
spray vaccination
poultry
- respiratory diseases, salmonella, coccidiosis, competitive exclusion
- mostly in the hatchery due to difficulties in the field
gel application
live coccidia and salmonella vaccines
- dropped onto chicks => preen themselves and ingest = vaccinated
in ovo vaccination
- light scans infertile eggs => removed
- fertile eggs gets vaccinated => makes hole in egg and inserts vaccine
- machine puts eggs into hatcher and incubates for 19 days
response to vaccines
- innate response is almost immediate
- humoral response: 10-14 days post primary vaccination, maximum immune response (vary w/ different pathogens)
- part of acquired immunity
- booster vaccines, stimulate max immunity (act as second exposure)
- secondary vaccinations boose response to be protected
- depending on the goal, life span of animal and pathogen => strategize boosters
vaccination hints
- vaccines are biologics (can be used in organic animals), regulated by USDA not a drug regulated by FDA
- organic animals can be vaccinated
- in CA, no antibiotics in birds => produce organic animals but can’t treat if get sick
- not all vaccines elicit a protective immune response (application, vaccine selection, agents vary)
- VACCINATION VS IMMUNIZATION
- follow label instructions
safety comparison
MLV
- can induce disease
- may cause aboriton
killed
- don’t cause disease
- safe in pregnant animals
recombinants
- safe and less/no secondary effects
Vaccine examples
bacterin
killed bacteria
- leptosporosis in cats/dogs
- salmonella in poultry
toxoid
inactivated bacterial toxin
requires 10-14 days to develop acquired immunity
acts as Agulent
antitoxins
horse or sheep derived serum Ab
passive imunization
imediately protective (not a real vx) => deliver antibodies
attenuated or modified live
whole organism, bacteria/viruses
the virulence is reduced by adaptation to other host/organism/environment
recombinants
live vector plus insert
immunity against Marek’s and Bursal Disease
vaccine failure
animal incubating disease (MDV)
- if infection happens before vaccination
- 10-14 days to respond to vaccine
- stress, immunosuppression => vaccine doesn’t act
ineffective vaccine (Africa)
- denatured by heat, UV light, “Cold-chain-storage” (live vaccines can’t be stored)
state of animal at time of vaccination
- maternal antibody interference, same in recently hatched chicks
- neutralize portion of vaccine
- pregnant animal depresses T-Cell function
- immunosuppression BVD virus, Se, Cu deficiency, stress
other possible vaccine failures
- high dose infectious inoculum may overcome immunity
- if vaccine has very high titer, you can overcome immune system and it can shut down
- application failure (common)
reasons for vaccination failure
- vaccine didn’t stimulate the correct type of immune response
- antibody (B cell response) = extracellular organisms; killed products
- cytotoxic cells (Tc cells) - intracellular agents
- MLV products stimulate CMI and antibody
- new infectious strain ( vaccine not cross protective)
- serotype diversity and no cross-protection
- difficult to target virus b/c it changes so quickly
- need to make vaccine similar to what’s happening in the field
passive immunity
transfer of antibodies from resistant animal (immune) to a susceptible (non-immune) animal
ex:
- passive transfer of colostral antibody (first milk)
- ruminants: lactogenic immunity
- antibody and soluble immune mediators in colostrum and milk during first few days of life that confer local protection in gut
- antiserum
- plasma transfusion => yolk contain antibodies
- yolk sac, passive transfer of maternal antibodies to the chicks (very important for certain diseases in poultry)
pros and cons of passive immunity
pros
- immediate protection against cell free infections and toxins
cons
- short lived (3 weeks at most)
- expensive (antisera)
- only involves half the immune response (humoral)
- interacts w/ early vaccination
what is the % protection from infections?
50%, 75%, 90% NONE ARE 100& PROTECTIVE
part of biosecurity progam
- best vaccine won’t make up for poor management
- vaccines are a management tool
- expensive!
- hence: remember the ‘triad of disease’
- important to reduce the infectious agent load in environment
- have good hygiene, reduce stocking density, biosecurity
- keep at risk animal segregated like neonates, newly hatched, and pregnant animals
vaccine strategies
exotic: DON’T VACCINATE
rapid diagnosis -> eradication -> quarantine -> compensation, stamp out, disposal -> surveillance -> biosecurity -> prevention
endemic:
rapid diagnosis -> control -> quarantine -> vaccination -> surveillance -> biosecurity -> prevention
adjuvants
enhancers of immune response
- enhancement of inflammation & stimulate individuals
- prolongation of antigen persistence
- delivery of co-stimulatory signals
- activation of cells of the immune system
