vaccination and public health

Question 1

Strategic aim of vaccines:

Answer 1

• selective protection of vulnerable
• eliminate disease
• eradicate disease

Question 2

elimination vs eradication

Answer 2

elimination = reduce number of infections, trasmission to humans, prevent outbreaks

eradication = no other reservoirs of the infection exist in animals or environment

Question 3

EX of elimination

Answer 3

tetanus, measles, diptheria

Question 4

EX of eradication

Answer 4

smallpox, polio

Question 5

Programmatic aim of vaccination:

Answer 5

• prevent deaths
• prevent infection
• prevent transmission
• prevent cases in certain groups

Question 6

How do you select a ‘high-risk group’?

Answer 6

• Risk of exposure higher (e.g. healthcare workers)

- Consequence of infection is more severe

Question 7

2 ex of passive immunity

Answer 7

• maternal antibodies

- injecting immunoglobulins

Question 8

2 ex of active immunity

Answer 8

• natural infection

- vaccine

Question 9

Why is active better than passive?

Answer 9

Lasts longer, immunological memory

Question 10

R0 =

Answer 10

Basic reproductive number. Average number of individuals directly infected by an infectious case during the infectious period in a totally susceptible population

Question 11

R0 is a property of…

Answer 11

Biological agent

Question 12

R0 is proportionate to…

Answer 12

• length of time case is infectious
• number of contacts
• chance of transmitting per encounter

Question 13

R =

Answer 13

effective reproductive number. Actual average number of secondary cases per primary case observed in a population

Question 14

R0 is usually … than R

Answer 14

> . this is because pop isn’t 100% susceptible

Question 15

In a homogeneous mixing population where s is the proportion susceptible R =

Answer 15

R = R0 x s

Question 16

R > 1

Answer 16

increases number of cases

Question 17

R = 1

Answer 17

epidemic threshold. stable

Question 18

R < 1

Answer 18

decreasing number of cases

Question 19

S* =

Answer 19

s* = 1/R0

Question 20

Herd immunity threshold H =

Answer 20

H = 1-1/R0 or 1- S*

Question 21

Herd immunity measures…

Answer 21

the indirect protection to the unvaccinated as well as direct effects of vaccination.

Question 22

Why is herd immunity important?

Answer 22

<100% vaccine efficacy
<100% vaccine uptake.
Some people have contraindications

Question 23

factors to consider when DECIDING and IMPLEMENTING a vaccine program:

Answer 23

• is the disease a public health problem?
• is immunisation the best strategy
• what will the net impact of a new vaccine be?
• possible negative effects
• additional resources
• impact on public perception
• const analysis

Question 24

Ex of passive vaccine

Answer 24

tetanus
gangrene
snake bite
hep B
rabies
Placental IgG
Colostral IgA

Question 25

Live vaccines

Answer 25

naturally attenuated or artificially attenuated

Question 26

‘naturally attenuated’

Answer 26

a related strain or species (e.g. cowpox and smallpox)

Question 27

EX of live vaccines

Answer 27

Oral polio, MMR, yellow fever, nasal influenza

Question 28

Non-living vaccines

Answer 28

killed whole organisms, antigenic components

Question 29

Advantages of dead/inactivated vaccines

Answer 29

• effective
• good stability in transport and storage
• safe for immunodeficient patients
• no risk for poliomyelitis

Question 30

Disadvantages of dead/inactivated vaccines

Answer 30

• doesn’t incude gut immunity
• boosters required
• injection
• higher community vaccine levels required

Question 31

Advantages of live/attenuated vaccines

Answer 31

• effective
• lifelong immunity
• induces immune response similar to natural infection
• indirect community immunisation
• oral
• boosters not required

Question 32

Disadvantages of live vaccines

Answer 32

Vaccine-induced poliomyiltis

• spreat to contacts w/o consent
• unsafe for immunodeficient individuals