vaccine

Question 1

What is an ideal vaccine?

Answer 1

• to produce the same immune protection which usually follows natural infection but w/o causing disease
• to generate long-lasting immunity
• to interrupt spread of infection

Question 2

Immunization: the deliberate provocation of an 1._______ immune response by introducing 2. _______ in the body.
It’s a procedure designed to increase concentrations of 3. _______ and/or 4.________ which are reactive against infection.

Answer 2

1. adaptive
2. antigen
3. antibodies
4. effector T cells

Question 3

Describe the 2 types of immunization

Answer 3

Passive immunity: protection is immediate

Active immunity: takes time (usually several weeks) to develop.

Question 4

Describe passive immunity:

1. Natural
2. Artificial

Answer 4

1. Natural: transplacental (mother to child) lg G

2. Artificial: injection of preformed antibodies

Question 5

Advantages & disadvantages of passive immunity

Answer 5

Adv:

• immediate protection
• can be used in immunosuppressed

Disadv:

• short period of protection
• potential allergic response if foreign antibodies given

Question 6

Desc. active immunity:

1. Natural:
2. Artificial:

Answer 6

1. Natural: following infections (immune to re-infection)

2. Artificial: vaccination– ensure large no. of antibodies & lymphocytes are avail before exposure to pathogen

Question 7

Does smallpox only occur in humans?

Answer 7

Yes

Question 8

Does smallpox cause a latent or persistent infection?

Answer 8

No

Question 9

How was the eradication of smallpox possible?

Answer 9

• smallpox vaccine was effective against all strains of variola virus
• high fidelity DNA polymerase, variola viruses were unable to undergo antigenic variation to escape immunity
• CD4 T cell-dependent neutralising antibodies to vaccinia antigens (pox virus family) are cross-reactive with smallpox antigens

Question 10

Features of effective vaccines

Answer 10

• safe
• protective
• gives sustained protection (must last for several years)
• induces neutralising antibody (prevent infection)
• induced protective t cells
• practical considerations: low cost per dose, few side effects, etc

Question 11

Selective vaccination for those at increased risk of disease:

Answer 11

• hep B
• influenza
• yellow fever
• rabies
• meningitis
• hep A
• measles
• strep. pneumonae

Question 12

What is herd immunity?

Answer 12

Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune.

Question 13

To achieve herd immunity, the % of individuals who need to be vaccinated depends on _____________________

Answer 13

the disease and the vaccines used.

Question 14

Herd immunity is only valid for _____________

Answer 14

transmissible infectious diseases eg. flu

Question 15

Why is herd immunity important?

Answer 15

• no vaccine is 100% effective

- immunocompromised people are unable to receive live vaccines

Question 16

What do vaccines generally contain?

And describe them.

Answer 16

1. Antigen(s) : any protein, peptide, substance, etc that stimulates an immune response (SPECIFIC to the pathogen of interest)
2. Adjuvant : a substance that enhances the immune response to a weakly immunogenic antigen (non-specific). It can also allow slow release of antigen to allow time for memory response to form

Question 17

Desc inactivated (killed) vaccines

Answer 17

• inactivation through heat or chemical fixation
• need multiple injections in initial course
• usually need boosters
• may be toxic
• need for adjuvant
• poor cell mediated immunity

Question 18

Examples of inactivated (killed) vaccines

Answer 18

cholera
plague
influenza
rabies
polio (salk)

Question 19

Desc live (attenuated) vaccines

Answer 19

They contain virulent human viruses that has been weakened.

Question 20

Examples of live (attenuated) vaccines

Answer 20

polio (oral vaccine)
mumps
measles
rubella
yellow fever
chickenpox
typhoid

Question 21

Advantages of live (attenuated) vaccines

Answer 21

• mimic natural infection
• produce large antigenic stimulus (organism can still replicate)
• generally induce T & B lymphocytes responses
• provide long-lasting protection

Question 22

Disadvantages of live (attenuated) vaccines

Answer 22

• may retain some pathogenicity
• may revert to virulence
• may not be safe to vaccinate the immunocompromised
• require a good cold chain

Question 23

Desc inactivated exotoxins (toxoid)

Answer 23

• inactivated by heat or chemicals

- intended to build immunity against the toxins & not the bacteria that produce the toxins

Question 24

Examples of inactivated exotoxins (toxoid)

Answer 24

tetanus toxoid

diphtheria toxoid

Question 25

What vaccine is most effective for those <2y.o. particularly vulnerable to bacterial meningitis?

Answer 25

conjugate vaccine

Question 26

Examples of conjugate vaccine

Answer 26

polysaccharides from Pneumococcus & meningococcal capsules

Question 27

Do polysaccharides from Pneumococcus have low levels of lg M?

Answer 27

Yes

Question 28

Do polysaccharides from Pneumococcus have memory?

Answer 28

No

Question 29

Desc subunit vaccines

Answer 29

- they present 1 or more antigens to the immune system w/o introducing pathogen particles - "subunit": antigen is a fragment of the pathogen

Question 30

The 2 methods of subunit vaccines

Answer 30

1. Present an antigen to the immune system using a specific, isolated protein from the pathogen 2. Put an antigen's gene from the targeted virus into another virus, to make a recombinant virus. The recombinant vector will express the antigen which is extracted.

Question 31

Example of a subunit vaccine

Answer 31

hep. B vaccine (yeast vector)

Question 32

Advantages of subunit vaccine

Answer 32

- cannot revert back to virulence - safe for the immunocompromised - can withstand changes in conditions (eg. temp., light exposure, humidity)

Question 33

Disadvantages of subunit vaccine

Answer 33

- reduced immunogenicity compared to attenuated vaccines - require adjuvants to improve immunogenicity - often require multiple doses/ boosters to provide long-term immunity - q costly - can be difficult to isolate the specific antigen

Question 34

RNA vaccine:

Answer 34

uses a copy of the mRNA that codes for the antigen of interest to produce an immune response

Question 35

3 types of RNA vaccine

Answer 35

1. non-replicating mRNA (mRNA encoding antigen + liposome) 2. in VIVO self-replicating mRNA (mRNA encoding antigen + the viral RNA replication machinery) 2. in VITRO dendritic cell non-replication mRNA

Question 36

Advantages of RNA vaccine

Answer 36

1. Safety - RNA vaccines are not made with pathogen particles of inactivated pathogen, so are non-infectious - RNA does not integrate itself into the host genome - RNA strand in the vaccine is degraded once the protein is made 2. Production: vaccines can be produced more rapidly in the lab

Question 37

Disadvantages of RNA vaccine + strategies to tackle them

Answer 37

1. May elicit an unintended immune rxn - strategy: to minimise, the mRNA vaccine sequences are designed to mimic those produced by mammalian cells 2. Delivery: free RNA in the body is quickly degraded - strategy: the RNA strand is incorporated into a larger molecule to help stabilise it or package into particles/lipsomes 3. Storage: need to be frozen or refridgerated