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CFB > WCS39 Immunization > Flashcards

WCS39 Immunization Flashcards

1
Q

HK Childhood Immunisation Program

A

Recent changes:

  • MMRV vaccine (2nd dose): P1 —> 18 months
  • 9-valent HPV vaccine (1st, 2nd dose): P5, P6

Vaccines NOT in HK universal programme:

  • ***Haemophilus influenza type b vaccine (very low incidence in HK)
  • ***Rotavirus vaccine (no deaths)

Vaccines in HK:

  1. BCG vaccine
  2. Hep B vaccine
  3. DTaP-IPV (Diphtheria, Tetanus, acellular Pertussis, Inactivated Poliovirus) vaccine
  4. Pneumococcal vaccine
  5. MMRV (新加Varicella) vaccine
  6. HPV vaccine (female)

(Mumps (腮腺炎)
Measles (麻疹)
Rubella (風疹, 德國麻疹)
Varicella (水痘))

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2
Q

Immunisation

A

Active: Antigen (whole / component)
- long-lasting response

Passive: Immunoglobulins (e.g. Zoster Ig, Hep B Ig)
- immune response last ***< few months

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3
Q

Vaccine types

A
  1. Live attenuated organism
    - OPV, **BCG, **Chickenpox, ***MMR
    - exception: Inborn errors of immunity (cannot give live attenuated)
  2. Killed whole organism
    - whole cell Pertussis, ***IPV, HAV
  3. Inactivated exotoxin
    - **diphtheria toxoid, **tetanus toxoid
  4. Subunit
    - acellular Pertussis, pneumovax
  5. Subunit conjugated (e.g. with protein —> make it more immunogenic)
    - **Haemophilus influenzae type B, **pneumococcal vaccine: PCV7, PCV10, PCV13
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4
Q

Live attenuated vaccines

A
  • Attenuated (weakened) form of “wild” virus / bacteria
  • ***Must replicate to be effective
  • Immune response ~ natural infection

Disadvantage:

  • Severe reactions possible (e.g. with babies with Inborn errors of immunity)
  • ***Interference from circulating Ab (↓ replication of live attenuated organism)
  • Unstable
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5
Q

Antibody and Live vaccines

A

Product given first

  1. Vaccine: wait 2 weeks before giving Ab
  2. Antibody: wait >3 months before giving vaccine

(E.g. Kawasaki Ab: high dose needed: 9 months separate from other vaccines)

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6
Q

Inactivated vaccines

A
  • Cannot replicate
  • ***Minimal interference from circulating Ab (∴ no need separate from IVIG)

Disadvantages:

  • Generally not as effective as live vaccines
  • Generally ***3-5 doses
  • Immune response mostly ***humoral (may have some T cell response)
  • Ab titre fall over time
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7
Q

Vaccination and Immunisation

A

Can have vaccination but no immunisation

  • if host did not mount immune response to vaccine
  • e.g. outdated vaccines

Primary vaccine failure: No response to vaccine at all
Secondary vaccine failure: have a response but lose it

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8
Q

Immunological challenges for new vaccines

A

Ability to generate memory B + T cells in host immune system

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9
Q

Vaccines

A
  1. Haemophilus influenzae type b vaccine
  2. Chickenpox vaccine (introduced in mid-2014)
  3. Rotavirus vaccine
  4. Influenza
  5. Pneumococcal vaccine
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10
Q

Barriers to overcome for universal Hib vaccination

A
  1. ***Disease burden low in
    - Hong Kong (incidence of Hib meningitis <5 yo: 3 per 100,000)
    - Singapore
    - Korea
    - China
  2. Cost of vaccines
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11
Q
  1. Haemophilus influenzae type b vaccine
A
  • Relatively low disease prevalence in East Asia
  • Conjugate Hib vaccine effective
  • Risk-benefit ratio for individual infant is overwhelming for vaccination
  • Issue of universal vaccination in HK not settled
  • ONLY used in ***private sector in HK with 50% coverage
    —> Hib disease incidence already dropped to <1 per 100,000 under 5 yo
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12
Q
  1. Chickenpox vaccine (introduced in mid-2014)
A
  • Composition: ***Live virus (Oka-Merck strain)
  • Efficacy: 95% (65-100%)
  • Duration of immunity: > 7 years
  • Schedule:
    1st dose: **1 year old
    2nd dose booster: **    18 months, introduced because of waning immunity
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13
Q

Varicella

A

Varicella epidemiology

  • Reservoir: Human
  • Transmission: Airborne droplet, Direct contact with lesions
  • Temporal pattern: Peak in ***winter and Early spring (US)
  • Communicability: 1-2 days before —> 4-5 days after onset of rash (may be longer in immunocompromised)

Pathogenesis:
Respiratory transmission of virus
—> Replication in **nasopharynx and regional LN
—> Repeated episodes of **viraemia (Primary, Secondary, etc.)
—> **Multiple tissues (e.g. skin), including **sensory ganglia, infected during viraemia
—> **Crops of rashes (with various stages: 四代同堂)
—> Red —> **Vesicles —> Crusting

Varicella complications:

  1. Bacterial infection of lesions
  2. CNS manifestations (***Reye’s syndrome, Cerebellar ataxia)
  3. Pneumonia (rare in children)
  4. Death ~1 in 60,000

Groups at ↑ risk of complications of Varicella:

  1. ***Normal adults (without prior chicken pox)
  2. Immunocompromised person
  3. Newborns with maternal rash onset within ***5 days before —> 48 hours after delivery
    - Ig not yet developed in mother even mother has viraemia

Congenital Varicella Syndrome:

  • Result from maternal infection during pregnancy
  • Period of risk may extend through first 20 weeks to pregnancy
  • Atrophy of extremity with skin scarring, low birth weight, eye and neurologic abnormalities
  • Risk ~2%
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14
Q

Zoster following vaccination

A
  • Most cases in children
  • Risk from ***wild virus 4-5 times higher than from vaccine virus
  • Mild illness without complications
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15
Q
  1. Rotavirus vaccine
A

Surface antigen

  • VP4 neutralisation antigen
  • VP7 neutralisation antigen
  • 1st gen live RV in late 1990’s linked with intussusception after licensure
  • 2nd gen live RV, necessary to do phase III trial
  • RV vaccines are safe and efficacious (but only in industrialised, middle income countries)
  • Not used in HK, most children manage diarrhoea very well —> minor morbidity
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16
Q
  1. Influenza vaccine
A

Recommended group:

  1. Children 6-23 months (reduce deaths / hospitalisation)
  2. Children 2-5 yo (reduce hospitalistion)
  3. Pregnant women (reduce severity)
  4. Elderly persons (>=65) in residential care homes
  5. Long-stay residents of institutions for the disabled
  6. Elderly >=65
  7. Persons with chronic illness
  8. Health care workers
  9. Poultry worker (prevent flu to spread among animal and human)

Challenges in vaccination in healthy children:

  • Influenza does not carry high mortality
  • only childhood vaccine that requires annual re-vaccination
  • uncertain time interval between vaccine availability and influenza starts to circulate
  • School Outreach Vaccination in HK from 2019/2020 for all primary schools and kindergartens
17
Q
  1. Pneumococcal vaccine
A

Over 92 different serotypes of pneumococci

Clinical diseases:

  1. ***Meningitis (serotypes 10A, 15B, 19F, 23F)
  2. ***Empyema (serotypes 1, 3, 5, 7F, 8, 19A)
  3. ***Necrotising pneumonia (serotypes 3)
  4. Septic shock

Efficacy (Not very good):

  • 8% against clinical pneumonia
  • 36% against CXR-positive pneumonia
  • Serotypes 3 in PCV13 vaccine is not effective —> no reduction in IPD (invasive pneumococcal disease)

PCV13 additional serotypes (比其他疫苗多左3, 19A, 6A serotype) cause significant disease burden even with vaccination

Mechanism:
Immunisation
—> Immunogenic response (Vaccine type specific Ab (***IgG))
—> Direct protection against Colonisation (e.g. Nasopharynx) + Disease

18
Q

Pneumococcal disease and vaccine

A
  • Heavy disease burden
  • PCV10 ~ efficacy to PCV13
  • 2+1 (2 priming dose + 1 booster) or 3+0 schedule —> similar impact
  • serotype replacement and vaccine failure (***serotype 3)
    —> need to add other previously non-covered serotype
  • surveillance of IPD (with ***serotype testing) is a MUST before and after PCV vaccination

Major barrier for using PCV is ***vaccine price

19
Q

COVID

A

Characteristics:

  • ↓ Type 1 IFN
  • ↑ TNF-α, IL-1/6/18
  • Lymphopenia indicator of disease severity
  • SARS Ab and memory B are short lived (<1 year)
  • ***Intranasal route may be better for COVID vaccine
20
Q

Evolution of immunisation program and prominence of vaccine safety

A 
Prevaccine
—> Increasing coverage
—> Loss of confidence due to adverse effects of vaccine
—> Outbreak
—> Resumption of confidence
—> Eradication
—> Vaccinations can be stopped

CFB (43 decks)

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