vaccination

vaccination def

having received the vaccine (getting the injection)

immunisation

receiving a vaccine and becoming immune to a disease as a result

2 functions of a vaccine

induce active immunity, immunological memory

requirements of a good vaccination - 7

gives same immune protection as natural infection without disease, safe, stable (temp), cheap cost, ease of administration, long term protection, interrupt spread of infection

4 vaccine types

live vaccines, inactivated vaccines, subunit, passive immunotherapy

live vaccines

whole pathogen for which virulence has been artificially reduced - attenuation

inactivated vaccines

whole killed organisms

5 types of subunit vaccines

toxoid, surface protein, viral vector, DNA, RNA

subunit vaccines

certain components of pathogens, can be purified or generated using recombinant dna tech

passive immunotherapy

taking antibodies produced in one host and inject into another

polio mechanism

CNS invasion - transmitted by faeces, virus enters blood in liver and spleen, and crosses brain blood barrier - causes fever, meningitis and paralysis

3 serotypes of polio

1 - brunhilde, 2 - lansing, 3 - leon

advantages of live attenuated vaccine

inexpensive, single oral dose, induces systemic and mucosal immunity, probably lifelong immunity

disadvantages of live attenuated vaccine`

can produce features of mild infection, unsuitable for immunosuppressed, unstable, can revert to virulent form

advantages of inactivated polio vaccine

contains 3 serotypes, prevent spread of virus to CNS, can't cause circulating vaccine derived polio virus

disadvantages of inactivated polio vaccine

subcutaneous injection - costs more, no effect on viral replication so can still be transmitted, less immunogenic to required adjuvants and boosters

adjuvants

enhance immune response to antigens

toxoid vaccine - tetanus

vaccine neutralises the toxin produced by tetanus bacterium, the neurotoxin causes muscle spasms and seizures

surface protein vaccine - hep B

surface protein is produced using dna tech and plasmid vectors, safer and cheaper to produce

dna vaccines

injecting nucleic acids which directly encode antigens, host cells take up and express to cause immune response

advantages of dna vaccines

no infectious agent, more stable, easy to manufacture, stimulate b and t cell responses, multiple antigen variants in a single vaccine

disadvantage of dna vaccines

concerns that incorporation of immunising dna can activate oncogenes

mRNA vaccine eg covid vaccine

RNA put in a lipid vesicle and directly taken up into cytoplasm, encode receptor binding domain of viral spike protein, requires careful long term storage

primary vaccine failure

individual fails to make an adequate immune response to initial vaccine - infection is possible anytime after

secondary vaccine failure

individual makes adequate immune response but immunity decreases over time, boosters are needed

herd immunity

more immune individuals in a population - less likely that a susceptible person will come into contact with an infected person

vaccine hesistancy

reluctancy to vaccinate despite vaccine availability, 1998 study claimed to show a link between MMR vaccine and autism