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Global Health diseases > Vaccine prophylaxis > Flashcards

Vaccine prophylaxis Flashcards

1
Q

Describe changes in global life expectancy

A
  • Around 100 years ago, life expectancy reached about 50-55 years
  • 1841:
    • Males: 40.2
    • Females: 42.2
  • In the US, 46% of deaths in 1910 were caused by infection. Now it is 3% of deaths
  • We do not succumb to infections so commonly anymore
  • Due to antibiotics, vaccinations, cleanliness, sanitation
  • Until 2020, infections in the western world were not a major cause of death
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2
Q

Compare causes of death between HICs and LICs

A

For every 1000 deaths in the world, 138 will be in high-income countries and 501 will be in low income countries.

People living in a low-income country are far more likely to die of a communicable disease than a noncommunicable disease.

Despite the global decline, six of the top 10 causes of death in low-income countries are communicable diseases.

Malaria, tuberculosis and HIV/AIDS all remain in the top 10.

Low income countries have much younger populations

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3
Q

Describe the accessibility of vaccines in the UK

A
  • There is massive global inequity in accessability of vaccinations
  • We have vaccinations for an array of diseases when we travel, but other countries do not
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4
Q

Could you name some diseases for which vaccines do not exist?

A

Hep C

Herpes Simplex

Universal influenza

HIV

EPV

Dengue

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5
Q

Could you name some general reasons as to why there are so many diseases for which vaccines do not exist?

A

Biology

New and emerging infections

Commercial

Logistics

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6
Q

What are the biological reasons as to why there are many diseases for which vaccines fo not exist?

A
  • “Escape” – development of mutations to avoid the immune system (eg influenza and HIV)
  • Evolution of protective mechanisms (eg S. pneumoniae and HIV)
  • Integration into the host genome (eg herpes simplex)
  • Dormancy in “immune privileged” sites (eg M. tuberculosis and Ebola)
  • Strain variation extending beyond immunological memory (eg dengue)
    • The protection against one serotype does not protect you from a; serotypes (antibody dependant enhancement in dengue)
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7
Q

What are the ‘new and emerging infections’ reasons as to why there are many diseases for which vacciens do not exist?

A
  • New infections are rare, but opportunities for zoonotic infections may be increasing
  • Zoonotic infections are on the increase. Very important source for new infections
  • Mostly contained in LMICs
  • Infections which only affect LMICs have been of little interest
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8
Q

What are the commercial reasons as to why there are so many diseases for which vaccines do not exist?

A

•Vaccines are expensive and complicated to develop

•Length and complication means that any vaccination becomes expensive

•Developing country problems are not commercially attractive

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9
Q

What are the logistical reasons as to why there are so many diseases for which vaccines do not exist?

A
  • Developing countries have limited infrastructure
  • Like the Pfizer vaccine must be stored at -80oc ]
  • Developing hot countries may not have the resources to cater for vaccine storage
  • The cold chain

Political / religious intervention

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10
Q

What are some of the new and emerging infections?

A

1983 - HIV

2002 – SARS-CoV-1 (Severe Acute Respiratory Syndrome Coronavirus virus)

2009 - H1N1 pandemic influenza (swine flu)

2014 - Ebola virus

2015 - Zika virus

2015 - MERS-CoV (Middle East Respiratory Syndrome Coronavirus)

2019 – SARS-CoV-2

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11
Q

What are some of the vaccine investment decisions?

A

Usually pharmaceuticals have a higher economic valie and a social value

Vaccines have a higher social value than an economic value

•Vaccines are not in the portfolio of large pharmaceutical countries

•Disincentives are the high costs of development and the demand for new vaccines at low prices

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12
Q

Which pathogens has the WHO listed as a priority?

A

Ebola virus

SARS/MERS

Lassa fever

Chikungunya

Zika

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13
Q

Why is there some trouble with vaccine coverage even though vaccines exist?

A

75% of the world’s population depends almost exclusively on plants for treating illnesses. (Homeopathic/traditional cures.

They arise because of their inability to access western medicine

30M children born every year are not adequately immunised

4.25 million deaths/yr from 6 major vaccine preventable diseases

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14
Q

Why do vaccines not work in the field?

A
  • vaccines must be manufactured and stored in the cold.
    • Many countries (LMICs) that are in dire need of vaccines are situated in the tropics.
    • It would be very difficult to store vaccines at the appropriate temperature (to not damage the vaccine and spoil the product)
    • MUST REMOVE THE NEED OF COLD CHAIN
  • Almost all vaccines are administered by needle and syringe
    • This must be eliminated because:
      • You need healthcare professionals
      • Needs proper disposal
      • Avoidance of reuse of needle and syringe
      • Costs of needle and syringe
      • Sterility of the syringe
  • Needs simplification
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15
Q

What is active immunisation?

A

Exposure to the antigen to generate an adaptive immune response. The response takes days/weeks to develop but may be long lasting- even lifelong

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16
Q

What is passive immunisation?

A

Providing pre-formed antibodies to protect against infection. The protection is immediate, but short-lived (days/weeks)

17
Q

What is post exposure prophylaxis?

A

Administered soon after a suspected infection, usually for lethal diseases.

Can comprise a combination of active and passive immunisation and chemotherapy

Risky approach

Could be involved with rabies treatement

18
Q

Give an example of passive immunisation, the advaantages and disadvantages

A
  • 1890- Development of Diptheria
  • Commercially produced in immunised horses and humans.
  • Monoclonal antibody technology

Key advantages :

  • Immediate protection
  • Effective in healthy & immunocompromised patients
  • More consistent response than vaccines

Disadvantages:

  • Quality control and uniformity of the product
  • Safety of production system
  • Repeated administration
  • Cost and availability
  • Short-lived protection
  • Escape mutants
  • Contamination through the horse/equipment
19
Q

What was the problem of administering convalescent serum as first choice treatment for COVID-19?

A
  • Convalescent= Antibodies from blood donated by people who recovered from the illness and hyper immunoglobulins are becoming treatments of choice for COVID-19

Problem?

  • Antibody response was low
  • It failed in the clinical trials in which convalescent serums were tested
20
Q

What is MTCT of HIV?

A
  • This is mother to child-transmission of HIV
  • From pregnant women to unborn foetus
  • At delivery
  • From woman to breast-feeding infant
  • Anti-retroviral drugs are highly effective,
  • but MTCT remains at ~11% across Africa.
  • The highest risk groups are:
  • •Women diagnosed with HIV late in pregnancy
  • (> 1st trimester)
  • •Patients with poor treatment compliance
  • •Those in areas where ARV resistance is increasing
21
Q

What is the purpose of neuralising monoclonal antibodies in mother to child transmisison of HIV

A

The objective of our research is to produce HIV neutralising mAbs for women in the peri-natal period and those who are breast-feeding newborn infants.

22
Q

Where is post-exposure prophylaxis used in?

A
  • Rabies
  • Tetanus
  • HIV
  • Hepatitis (A, B and C)
  • Ebola
23
Q

What is rabies?

A
  • Rabies is a zoonotic viral disease (a virus that is transmitted to humans from animals).
  • The disease affects domestic and wild animals, and is spread to people through close contact, usually saliva, via bites or scratches.
  • Dogs are the main host and transmitter of rabies. Bats (Americas and W. Europe) and other wild carnivorous species are also responsible.
24
Q

How does the rabies virus cause illness?

A

•The virus spreads along nerves towards the spinal cord and brain. First symptoms usually appear after 1–3 months, after which death is inevitable:

–Furious rabies - hyperactivity and excited behaviour, fear of water and sometimes air movement. After a few days, death occurs by cardio-respiratory arrest.

–Paralytic rabies - gradual muscle paralysis starting at the site of the bite; a coma slowly develops, and eventually death.

25
Q

How many people die of rabies per year?

A

More than 50 000 people

95% in Asia and Africa

26
Q

What are the control measures against rabies?

A
  • Animal reservoirs
    • Sterilisation
    • Euthanisation
    • Vaccination
  • Humans
    • Education
    • Post exposure prophylaxis
    • Vaccination

Post exposure prophylaxis is effective if the treatment is started immediately after exposure

27
Q

What are the benefits of rabies post exposure prophylaxis?

A

Post exposure prophylaxis inlcudes cleansing, vaccination & rabies immunoglobulin

around 270 000 people’s lives are saved by PEP

28
Q

Disadvantages of rabies PEP?

A
  • UNAFFORDABILITY
    • Vaccinated human donora = $300 per dose
    • Immunised equine sources = $7 per dose
  • Limited availability
  • Batch to batch differences
  • Contamination with blood derived products
  • Two teir sysstem for product availability
  • Ethical issues (use of animal products)
29
Q

What is Ebola?

A

Ebolavirus was first discovered in 1976 after outbreaks in Sudan and Zaire.

The virus causes a haemorrhagic fever (fever with bleeding):

  • Early symptoms are fever, severe headache, muscle pain; diarrhoea, vomiting, unexplained bleeding.
  • Disease progression to extensive bleeding, bleeding skin rash and blisters.
  • Up to 90% of patients die, usually from the consequence of massive bleeding.
30
Q

What is the transmission of ebola?

A

natural reservoir of Ebolavirus is unknown, but may be in bats.

Ebolavirus can be caught from infected animals or humans.

Ebola is spread through direct contact with body fluids – vomit, blood, saliva, tears…

During outbreaks, the disease can spread quickly within hospital, particularly amongst healthcare workers.

Dense living conditions and traditional burial practices also contribute to transmission.

31
Q

What are the responses to ebola?

A
  • Community engagement
  • good outbreak control relies on interventions like case management , sufficient surveillance , safe burials and social mobilisation (identifing people who have been infected with ebola)
  • Early supportive care with rehydration, symptomatic treatment improves survival.
  • Reducing the risk of wildlife-to-human transmission from contact with infected fruit bats or monkeys/apes and the consumption of their raw meat.
  • Reducing the risk of human-to-human transmission from direct or close contact with people with Ebola symptoms, particularly with their bodily fluids.

Outbreak containment measures including prompt and safe burial of the dead, identifying people who may have been in contact with someone infected with Ebola, monitoring the health of contacts for 21 days, the importance of separating the healthy from the sick to prevent further spread, the importance of good hygiene and maintaining a clean environment

32
Q

Give an example of a PEP pertaining to ebola?

A

Experimental monoclonal antobodies ZMapp

Cocktail of 3 amonoclonal antibodies that were shown in rhesus monkeys to prpotect against ebola virus

Administered to 9 patients as PEP, 6 survived

ZMapp mAbs are non-competing and bind across Ebolavirus GP1 and GP2

ZMapp mAbs are made in tobacco plants (highly scalable and economic)

33
Q

What is the vaccination ring with regards to ebola?

A

Vaccination of contacts

For every index case included in the study we define contacts as individuals who, within the last 21 days, lived in the same household, were visited by the index case after the onset of symptoms, or were in close physical contact with the patient’s body or body fluids, linen or clothes.

Contacts-of-contacts include the neighbours, family or extended family members to the nearest geographic boundary of all contacts, plus household members of any high-risk contacts.

34
Q

How was president trump treated for COVID

A

PEP

Dexamethasone (steroid to dampen the inflammator response)

Revdesivir (anti-viral originally developed for Ebola)

Regeneron monoclonal antibodies (a cocktail of two SARS-CoV-2 neutralising antibodies)

35
Q
A
36
Q

Why have vaccines companies used completely new platform technologies for the world’s most urgently needed vaccine?

A

Key Advantages:

  • Speed
  • Scalability
  • Adaptability
  • Commercial advantage
  • Opportunity to establish new technology

Major Risks:

  • Unfamiliarity
  • Public acceptance
  • Global accessibility

Global Health diseases (30 decks)

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