Lectures Summary PGZ
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:
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, - 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
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, 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
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, ➔ 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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