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Samenvatting eerste 7 taken PGZ2024: Disease and Prevention
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De eerste 7 taken van PGZ2024: Disease and Prevention uitgewerkt volgens de leerdoelen.
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Taak 1: VaccinationVaccination is a way to produce active immunity. Vaccines contain antigens that stimulate the immune system
to produce an immune response.
There are two basic types of vaccines.
1. Live, attenuated (verzwakt): live vaccines are derived from “wild” viruses or bacteria. These wild
viruses or bacteria are attenuated (weakened) in a laboratory (the measles virus).
2. Inactivated: inactivated vaccines are not alive and cannot replicate. These vaccines cannot cause
disease, even in an immunodeficient person (a very vulnerable person).
Inactivated vaccines include:
- whole-cell inactivated vaccines (e.g., polio, hepatitis A, and rabies vaccines) à bacteria or viruses that
have been killed through a physical or chemical process.
- subunit vaccines (e.g., influenza and pneumococcal vaccines) à a portion of the bacteria or virus.
- toxoids (e.g., diphtheria and tetanus toxoid) à are made using inactivated toxins produced by bacteria.
- recombinant vaccines (e.g., hepatitis B, human papillomavirus [HPV], and influenza à are produced
by recombinant DNA technology.
Good to know that there are types, but you don’t have to come up with them
Immune system
The immune system develops a defense against antigens, which are substances that can stimulate the immune
system. This defense is known as the immune response and usually involves the production of:
- Protein molecules (immunoglobulins or antibodies, the most important component of humoral
immunity) by B lymphocytes (B cells)
- Specific cells, including T lymphocytes (also known as cell-mediated immunity)
2 basic mechanisms: passive and active immunity.
- Passive immunity is protection by antibody or antitoxin produced by one animal or human and
transferred to another. Passive immunity provides immediate protection against infection, but that
protection is temporary.
Passive immunity can also be acquired through the transfusion of blood products.
Example: when an infant receives antibodies from the mother. An infant will then have the same type of
antibodies as the mother. The infant is then protected from certain diseases within the first few months after
birth.
- Active immunity is protection produced by a person’s own immune system. The immune system is
stimulated by an antigen to produce antibody-mediated and cell-mediated immunity. Unlike passive
immunity, which is temporary, active immunity usually lasts for many years, often for a lifetime
o A way to acquire active immunity is by surviving an infection.
Immunologic memory = the fact that protection persists for many years after infection. After
the immune system has been exposed to an antigen, B memory cells continue to circulate in
the blood and when re-exposed to the antigen, the memory cells begin to replicate and rapidly
produce antibodies to restore protection.
o Another way to produce active immunity is by vaccination. The recipient is not subjected to
the disease and its potential complications. A vaccine contains antigens that stimulate the
immune system to produce an immune response.
,Herd immunity
Herd immunity = the resistance of a group attacked by a disease, due to the
immunity of a large proportion of its members and the consequent reduction
in the likelihood of an infected individual coming into contact with a
susceptible (vatbaar) individual.
Herd immunity can be achieved by mass immunization against infections
that are transmitted directly from person-to-person (e.g., measles, pertussis,
or influenza)
Other factors that infect herd immunity: how well the vaccination uptake is
in different population groups (bible belt).
Vaccination degree depends on the disease.
Theoretical developments in the concept of herd immunity
1. An ideal vaccine should be highly immunogenic and would
confer solid immunity against infection to all recipients.
However, when a vaccine does not grand solid immunity, the
threshold level of vaccination required to protect a population
will increase.
2. In a heterogeneous population, the R0 should account for the
factors that affect the interaction of various groups in a
population. Groups that are highly interconnected will
dominate transmission leading to a higher value of R0.
3. Simple results will no longer follow if vaccination coverage
differs depending on the risk behaviors of the groups. For example, if every highrisk person in a
population infects four individuals (R0= 4, so vaccine coverage = 75%) and every individual in
low-risk group infects only one person (R0=1, so vaccine coverage = 0%), outbreaks in theory can,
most cost-effectively, be prevented by vaccinating 75% of the high-risk group
4. Freeloaders – people who wish everyone else is vaccinated except themselves, they take advantage
of herd immunity without taking the trouble of getting the vaccine.
Effective transmission:
Contagiousness (pathogen) and susceptibility (host)
- Contagiousness (besmettelijkheid)
Basic reproductive rate R0
R0 = B x c x D
B = chance of transmission
c = number of newly infected/time
D = duration of infectious period
Infection will: disappear if R<1
become endemic if R=1
become epidemic if R>1
- Susceptibility (vatbaarheid)
o Personal immunity
o Herd immunity
, Scientists use R naught or R0 to estimate how many people one sick person is likely to infect à how contagious
is a disease?
Concerns about vaccination & prevention
The role of social media
à Confirmation bias
Health literacy à easier to understand?
Vaccination hesitancy
Polio à examples of people dying, now that is less. Risk of vaccination is perceived differently than earlier. You
won’t experience the consequences directly à makes it difficult.
Social media have a wide reach and can therefore serve as important tools for spreading information.
Social media such as Facebook and Twitter can play an important role in building the information capacities of
the public, making science and scientific decision-making processes and scientific decision-making processes
more widely accessible to the public, and enabling public participation in the use of science.
For example, comparative effectiveness information on effects, side effects, risks, and costs of different
prevention and treatment options can be widely disseminated using social media.
à The WHO uses tweets to reach out to global publics with health information, reaching over 900,000
‘followers’
- Social media as resources for listening
- Social media as avenues of expression and performance
- Social media as advocacy and activist resources
As a result of the Internet and social media, private and public concerns about vaccinations have the potential to
spread virally around the world in a rapid, efficient, and vibrant way.
It seems worthwhile that public health websites be easy to find and use, attractive in their presentation, and easy
to provide the information, support, and advice that the seeker is looking for. This is especially true when less
informed individuals need reliable information about the risks and benefits of vaccination à health literacy
How to handle a social media campaign?
Understandable, visualized, frequencies, address the facts of a campaign, focus on the facts.
Fuzzy trace theory?
Challenges/opportunities that we face in global immunization
Low-income countries and vaccination possibilities
Relocation of polio
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