Disease and Prevention PGZ2024 Lectures Exam Summary
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Course
PGZ2024
Institution
Maastricht University (UM)
This is a summary of the all the lectures that take place in the Disease and prevention module which is part of the Health sciences and public health bachelor. It includes the main aspects and highlights of each lectures but also has enough details for you to not only pass the exam but also to get ...
Prevention by Vaccination:
➔ History of vaccinations:
- In the past, the chance of getting an infectious disease was much bigger than
nowadays (people used the same water for sewage for cooking)
- The mortality due to infectious diseases declined drastically through time (not due
to vaccines or antibiotics, but due to our better hygiene measures)
- WW2 → first use of antibiotics and first use of vaccines (oral vaccines against
polio)
➔ First vaccine was done for smallpox: discovery:
- Smallpox → Jenner found out that milkmaids that were in contact with cows
when milking them were immune to smallpox. (Contact with pus from cowpox
lesions → Inoculation/vaccination → protection against smallpox)
- Cowpox vaccination gave immune to human smallpox infection (vaccination in
the form of scratches on the arm)
- Basic principle of the vaccination → Inoculation with mild disease could give
protective immunity against serious diseases + Mimicking infection leads to
protective immunity against future infections
➔ Can all infectious diseases be eliminated if everybody gets vaccinated:
- Not always → We can not eradicate tetanus from the world
- To fully eradicate a disease, it has to be in a human or animal reservoir but in the
case of tetanus, the infection is in the soil and we can not control it
➔ Facts about vaccines:
- It takes 6 to 18 years to develop and get the vaccine on the market
- It takes up to 3 years to produce a vaccine.
- Few pharmaceuticals that produce vaccines. (Costs a lot of money and takes a lot
of time)
- In COVID 19 →
- We knew what kind of vaccine we needed from the MERS corona
- Normally the clinical trials happen after each other, but in the case of corona the
clinical trials overlapped and production happened under risk, production
happened during phase 3 of clinical trials to accelerate time.
- Approval happened during the clinical trial phases so it was quick
➔ Infectious disease control:
1
, - Effective transmission: when can a disease make a host sick. (Effective
transmission = Contagiousness of the pathogen + susceptibility off the host)
- Reproductive rate (R0): number that expresses the contagiousness of a disease.
Insert pic
- How contagious is a disease: Scientists use the R0 to estimate how many other
people one sick person is likely to infect.
- The higher the R0, the more contagious a disease is
- Covid-19 has a R0 of around 2.
How do we know if a population is vaccinated enough:
- We need the R0
Example of measles:
- R0= 18
- 1-1/18= 94.5% vaccination coverage
needed to not have another outbreak of
the disease
- However some people are
immunocompromised and cannot be vaccinated
- When enough people are vaccinated → Herd
Immunity, then the immunocompromised people are safe. (Protected by the herd)
➔ Immunological basis:
- Part of an antigen is given to a person through the vaccine → then people develop
an antibody response.
- Antigen trigger → Immune response: Temporarily or Memory.
➔ Different kinds of immunization:
- Passive immunization: we are given the antiserum/antibodies. Provides immediate
but short-lived protection, lasting several weeks to some months.
- Active immunization/Vaccination: Live attenuated vaccine or dead vaccine (small
dead part of the virus). We are given the antigen to generate an immune response,
protection lasts longer.
➔ Vaccines ingredients:
1. Antigen: parts of one or more pathogens
2. Adjuvans: improving immunogenicity. E.g, aluminum hydroxide (AIOH)
3. Preservatives and stabilizers: thiomersal (can not be given to children below 6) or
phenoxyethanol
2
, 4. Others/traces: antibiotics, (chicken) protein, cell material
➔ Vaccination Cost-benefit balance:
➔ National vaccine program:
- The national vaccine program in the Netherlands has so many more vaccines than
40 years ago due to the International vaccine development. More children are
being protected from these vaccines.
- Who decides what is in the national vaccine program:
- Advisory council of the government giving advice to the ministry of health
- The Ministry of Health takes the decision after the advice (Advice based on
evidence..)
- Themes of advice: optimum healthcare, prevention, healthy nutrition,
environmental health, healthy working conditions, and innovation and the
knowledge infrastructure. Advice → based on the state of science and evidence
- Permanent committee comes up with the “vaccination policy”
- In the NL, enrolling in the vaccine program is not mandatory but voluntary but in
Italy it is mandatory to enroll in the vaccine program.
Health Council: Criteria of vaccines to be included in the National Vaccine
programs:
1. Disease burden (individuals or group)
2. Efficacy and effectivity vaccine (reduction disease, vaccination coverage)
3. Safety: side effects
4. Acceptability - health costs - health benefits vaccine in individual/population
5. Acceptability - health costs - health benefits programme in individual/population
6. Expediency - cost effectiveness
7. Priority - potential urgent problem
3
, ➔ When and to whom give the vaccines:
- Children in the National Immunization programme (free)
- To patients: with influenza, pneumococcal disease, meningococcal disease
- To Risk groups: Hepatitis B
- To Travelers: Hepatitis A and B, rabies (paid)
- In case of an Outbreak: Hepatitis A, measles
➔ Meningococcal disease vaccination: What is meningococcal disease:
- Meningococcal disease occurs as a result of an invasive bacterial infection caused
by Neisseria meningitidis, which is commonly known as the meningococcus.
(Bacteria in throat that can be transmitted through sneezing)
- Chain of infection (Transmission): Meningococcal is being spread by aerosols
(possible disease spread)
- Many teenegers are carriers of the disease (1 in 3). Insert image. There are many
invisible and asymptomatic infections
- There are different types of Meningococcal capsules: MenA, MenB, MenC,
MenW, MenY and developing human cell
Why control measures are needed for MenW:
Although number of cases is low, still considered public health emergency,
- Because the numbers are increasing rather than decreasing (Rapid increase in
MenW)
- High virulent strain (high burden of disease)
- International experience causing outbreaks
- ACWY vaccines → excellent protection expected after a single dose
➔ Vaccine strategy: Strategy is to target carriers with conjugate ACWY vaccine:
- Plan to immunize adolescents
- Vaccinating older cohorts in catch up will accelerate control
➔ Situation of meningococcal in the NL:
- Same as the UK, cases among teenagers and those over 45 and not only children
- Infectious disease control measure: decision by GGD of local government and
Expertise center (Outbreak management team) will discuss with the national
government. RIVM interact with other countries or the WHO if there is also a
danger to other countries from outbreak in the NL
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