Immunisations

Question 1

What are the objectives of immunisation

Answer 1

To protect individuals from a disease (either from infection or from mortality)
To protect populations
To achieve herd immunity - to stop transmission
Eradication of disease
Decrease severity of disease - reducing hospitalisation
Indirect protection - vaccinating mother to protect baby e.g. whooping cough
To protect selected high risk groups

Question 2

What is the difference between eradication and elimination

Answer 2

Elimination: removal from an area (no longer endemic) - but can still get imported cases.
Eradication - no cases

Question 3

Difference between vaccination and immunisation

Answer 3

Vaccination = to give a vaccine - may not result in immunity
Immunisation - to artificially confer immunity

Question 4

2 mechanisms of immunisation

Answer 4

Active
Passive

Question 5

Different types of vaccines

Answer 5

Live unattenuated
Live attenuated
Killed whole organisms
Disrupted toxin
Antigenic components from organisms
Manufactured virus like particles
Conjugated vaccine

Question 6

Example of live unattenuated vaccine

Answer 6

Original cow pox innoculations - body generates immunity to small pox not just cow pox (and cow pox doesn’t make them that sick)

Question 7

Examples of live attenuated vaccines

Answer 7

MMR
BCG
Oral Polio vaccine

Question 8

Example of killed whole organism vaccine

Answer 8

Injectable polio

Question 9

Example of disrupted toxin vaccine

Answer 9

Tetanus toxoid

Question 10

Example of antigenic components from organisms vaccine

Answer 10

Flu
Hep B
Covid19

Question 11

example of manufactured virus like particles vaccines

Answer 11

HPV

Question 12

What is a conjugated vaccine

Answer 12

combines a weak antigen with a strong antigen as a carrier so that the immune system has a stronger response to the weak antigen
(particularly in vaccines for children e.g. HIB)

Question 13

Why is eradication difficult to achieve

Answer 13

Expensive
Has to be a global effort
Only works if vaccines stop transmission rather than reducing severity
Needs peace (not war)
Needs political will

Question 14

What are nasal vaccines good for

Answer 14

Reducing airborne transmission

Question 15

What factors effect susceptibility to disease

Answer 15

Immunity - previous natural infection or previous immunisation

Age - immature immune systems and waning immunity (the older you get the less able you are to produce a non specific response - rely on memory and targeted response

Immunocompetence - immune deficiency syndromes, immunosuppressive treatments, steroids, intercurrent infection

Question 16

Why will 100% personal protection never be achieved with immunisation

Answer 16

<100% Vaccine efficacy due to:
- handling
- temperature
- optimal age for vaccination
- Boosters (lack of completing course)
- Optimal dose etc.
- Mutation of pathogen
- effective administration

<100% vaccine uptake due to:
- public perception
- misinformation
- accessibility
- culture
- production - enough
- religion (vaccines containing pork etc.)
- medical conditions/contraindications preventing immunisation

Question 17

What does R0 depend on

Answer 17

Organism characteristics: infectivity, duration of infectiousness
Population characteristics: Mixing patterns, demographics, population density

Question 18

What is the effective reproduction number (R)

Answer 18

the average number of secondary infections produced by a typical infective agent.
In a homogenously mixing population where s is the proportion susceptible: R=R0xs

Question 19

What is the epidemic threshold?

Answer 19

If R>1, the number of cases increases
If R <1, the number of cases decreases
R=1 is the epidemic threshold.
To achieve elimination we need to maintain R<1

Question 20

What is the critical proportion susceptible (s*)

Answer 20

The threshold at R=1, defines the critical proportion susceptible, s*
1=R0 x s
S* = 1/R0

Question 21

What variable effects herd immunity

Answer 21

the greater the infectivity (reproductive rate) of a disease, the higher the immunisation rate needed to achieve herd immunity

Question 22

Herd Immunity Threshold (H)

Answer 22

H = 1-S*
so
H=1-1/R0
Measles has one of the highest herd immunity thresholds (92-95%) whereas influenza has one of the lowest (33-44%)

Question 23

What is vaccine efficacy (VE)

Answer 23

AR (unvaccinated)

x100
(AR = attack rate)

Question 24

Decision making process for deciding whether to implement a new immunisation programme

Answer 24

• Disease burden (is it a PH problem) - no. of cases, morbidity, mortality
• Is immunisation the best strategy for controlling the disease (is there another way and then analyse cost, benefit, effectiveness, safety, feasibility, practicality of each method compared to immunisation)
• What will be the net impact of introducing a new vaccine (impact on disease burden - vaccine effectiveness; vaccine safety (adverse effects, monitoring systems, vaccine damage, compensation schemes)
• How well is our current immunisation programme working? (will introduction of a new vaccine make things better or worse, fit in with current schedule)
• How much disease will be prevented (depends on age-specific disease burden in relation to age of immunisation, vaccine effectiveness & coverage)
• what are the possible negative effects of the new vaccination programme? (vaccine risk, possibility of programme errors, risk in strategy, vaccines interfering with each other)
• what resources are needed
• what is the impact on public perception (will adding new vaccine damage perception of immunisation)
• is the vaccine a good investment (cost of introduction - one off and ongoing costs, economic analysis: cost-benefit compared to other interventions, opportunity cost)

Question 25

What to consider when implementing vaccines (short answer)

Answer 25

* Cost benefit analysis * demand/need * infrastructure * acceptability * purpose of vaccination

Question 26

What to consider when implementing a new immunisation programme

Answer 26

* Who to vaccinate (depends on aim - to protect vulnerable, contain outbreak or eradicate disease); group with greatest morbidity/mortality; window of opportunity for prevention (e.g. preexposure); optimum effectiveness; vaccine efficacy in different age groups * How to implement (Pilots, phased introduction, global immunisation) * When to vaccinate (greatest impact on disease burden e.g. seasonal diseases; things to do to maximise uptake e.g. term time if school aged, multiple vaccines for rapid protection of most vulnerable etc.)

Question 27

Examples of international immunisation programmes

Answer 27

EPI - expanded programme on immunisation GPEI - global polio eradication initiative GAVI (global alliance for vaccines and immunisation) COVAX

Question 28

Role of WHO for immunisations

Answer 28

- makes recommendations for policy - supports less able countries with strategy implementation - works through the international health regulations

Question 29

Diphtheria

Answer 29

Caused by Corynebacterium diphtheria Primarily infects the throat and upper airways Produces a toxin affecting other organs 2 types: - disease of throat and tonsils - skin ulcers especially in tropical countries most cases in unvaccinated children fatal in 5-10%

Question 30

Tetanus

Answer 30

Clostridium tetani produces a toxin that causes painful muscle contractions, making it hard to open the mouth and swallow (lockjaw) Neonatal and maternal tetanus = most common & serious Mortality reducing due to TTCV (tetanus toxoid containing vaccine) MNTE: Maternal & Neonatal Tetanus Elimination Initiative, launched 1999 (immunisation, clean deliveries & surveillance)

Question 31

Polio

Answer 31

Viral. V infectious. Mostly effects children <5 Person to person spread, mainly faecal-oral or sometimes contaminated food/water Intestine --> nervous system --> paralysis 1/200 irreversible paralysis. 5-10% die. Cases dramatically reducing - oral polio vaccine multiple doses for children in 2020 only Afghanistan and Pakistan were still polio-endemic

Question 32

Measles

Answer 32

Viral. Airborne transmission. Prior to vaccine in 1963 major epidemics every 2-3 years. Most deaths = complications --> most common in <5 and >30. Blindness, encephalitis, severe diarrhoea & dehydration, ear infections, pneumonia Severe more likely in malnourished, insufficient vitA, immunocompromised (HIV/AIDS etc.) 95% in LICs Measles vaccines - one of the best buys in PH

Question 33

Haemophilus Influenza B (HiB)

Answer 33

Bacterial, transmitted through resp tract. Severe pneumonia, meningitis etc. <5. 2-3 million serious, 386000 deaths p.a. Needs prompt lab investigation prior to Abx. Abx resistance increasing Vaccine - only PH tool: in >100 countries so far. Hib conjugate vaccine recommended (available monovalent or combined with DTP and others)

Question 34

Hepatitis B

Answer 34

Viral. Transmission: blood & sex Life threatening & can lead to chronic liver disease & > death from liver cirrhosis & liver cancer 2billion infected Vaccine 95% effective preventing infection & chronic consequences Only given to high risk groups in UK atm.

Question 35

Yellow Fever

Answer 35

Caused by flavivirus. Mosquito vector. Cases severely underreported. Varies from mild fever --> fatal multi-organ failure 200,000 cases & 30,000 deaths p.a. Vaccine: life long immunity, used in travellers & outbreak. Mosquito control programmes - lapsed in some areas Strategy to Eliminate Yellow fever Epidemic (EYE) by GAVI, WHO, UNICEF etc to face challenging epidemiology, resurgence of mosquitos, increased risk of urban outbreaks and spread. Aims to protect at risk populations, prevent international spread, contain outbreaks rapidly

Question 36

Vaccines at 8 weeks

Answer 36

Diphtheria, tetanus, pertussis (whooping cough), polio, Hib, hep B MenB Rotavirus

Question 37

Vaccines at 12 weeks

Answer 37

Diphtheria, tetanus, pertussis, polio, Hib, hep B Pneumococcal Rotavirus

Question 38

Vaccines at 16 weeks

Answer 38

Diphtheria, tetanus, pertussis, polio, Hib and hepatitis B MenB

Question 39

1 year old vaccines

Answer 39

Hib, MenC Pneumococcal MMR MenB

Question 40

Eligable children each year from September vaccine

Answer 40

Influenza

Question 41

~3 years 4 months vaccines

Answer 41

Diphtheria, tetanus, pertussis, polio MMR

Question 42

Boys and girls aged 12-13 vaccines

Answer 42

HPV

Question 43

14 years vaccines

Answer 43

Tetanus, diphtheria, polio Meningococcal A,C,W,Y

Question 44

65 years old vaccine

Answer 44

Pneumococcal & Shingles

Question 45

>65 years annual vaccine

Answer 45

influenza

Question 46

70-79 years vaccine

Answer 46

shingles

Question 47

Expanded Programme on Immunisation (EPI)

Answer 47

Launched following success of smallpox vaccine. Aims to ensure vaccination for all children <1. Measles, whooping cough, diphtheria, tetanus, polio, TB now also vitamin A, HBsAG B (HepB), Hib, Yellow fever

Question 48

Strategies to achieve global vaccination targets

Answer 48

Integrate vaccination with primary healthcare services Expand vaccination coverage to eligible population Ensure regular supply of potent vaccines Strengthen the cold chain Training & capacity building of health personnel Promote community participation Incorporating health education Ensure logistic support Monitoring & evaluation Research

Question 49

What is the vaccine cold chain pathway

Answer 49

Need to maintain the same temperature throughout the chain - Manufacturer - National storage facility - Regional hospital - Health centre - Vaccination outreach

Question 50

Challenges in implementing vaccination programmes (globally)

Answer 50

Cold chain management Education (public awareness/support, culture, suspicion of the west Mistrust Corruption Cost Lack of skills in healthcare workers Lack of training Supply chain Access - vaccination on a market day, difficult to access communities etc

Question 51

6 Objectives of the global vaccine action plan

Answer 51

1. All countries commit to immunisation as a priority 2. individuals & communities understand the value of vaccines & demand them as their right and responisbility 3. benefits of immunisation equitably extended to all people 4. strengthen immunisation systems as part of a well functioning health system 5. ensure immunisation programmes have sustainable access to predictable funding, supply, & innovative technologies 6. Country, regional, and global research and development innovations maximise benefits of immunisation.