Chapter 9: Vaccine development
What is a vaccine?
A vaccine is a biological product. The purpose is to develop protection against infectious diseases;
irreversible immunological reaction; in healthy persons (prophylactic vaccines are given to healthy
persons); and in large populations. The composition is a microbial component (an antigen), adjuvants
(to help to get a good immune response) and stabilisators (to keep the vaccine stable).
Difference between drugs and vaccines
Drug Vaccine
Purpose Treatment of disease Prevention of (infectious) disease
Target population Sick persons Healthy persons
Level of interaction General interaction with the body Specific interaction with the immune system
Means Corrects what went wrong Enhances protective capacity
Immune system Prevent immunological reaction Immunological reaction wanted
Adverse events Sometimes Often local, seldom serious
Dose Individual dosing Dose defined per age group
Advantage Personal cure Personal protection and group protection
The adverse events after a vaccine is often local. For example: your arm will be stiff after the tetanus
vaccine. You are not really sick or ill from the adverse events.
Why develop vaccines?
Vaccines have saved millions of lives. Annually 6 million deaths are prevented. Eradication of
smallpox, so 350 million new victims were identified and 40 million deaths were avoided. What is the
return on investment? For every dollar invested, the return on investment is 40 dollars. However,
evidence shows that effect of vaccines stretches beyond prevention of illness and death!
Vaccine types
There are different vaccine types dependent on the antigen type. The type vaccine influences how
the vaccine is used (target population, etc.), the storage and the administration.
Vaccine types – Whole pathogen vaccines
The oldest form of vaccines are the whole pathogen vaccines. In these types, you use a whole
pathogen (bacterium or virus) and you make a vaccine from this. This can be an inactivated vaccine
or a live-attenuated vaccine. In the inactivated vaccines, the whole bacteria or viruses are inactivated
(by using heat or chemical components). So, there will be no replication of the pathogen. This means
that there will be no disease (also not for immune-compromised people) and not always a strong or
long-lasting immune response. This is a very safe type of disease! The immune response is not that
strong, because the virus is not replicating. The disadvantages are:
May not always induce an immune response at first dose
Response may not be long-lived, requiring several doses of vaccine
So, the inactivated whole pathogen vaccines have a less strong immune response compared to live
vaccines. The advantages are:
Have no live components, so no risk of inducing the disease
Safer and more stable than LAVs
These kind of vaccines have an excellent stability profile. Examples of these kind of vaccines are the
SARS-CoV-2 (Sinovac, Sinopharm), the polio vaccine (inactivated, Salk) or the hepatitis A virus
vaccine. Poliomyelitis is an inactivated polio vaccine by Jonas Salk. It consists of a mixture of three
polioviruses (serotype 1-3). It is produced from wild-type poliovirus strains of each serotype and
inactivated with formalin. It is developed in the 1950s and it can be used in combination with other
vaccines: diphtheria, tetanus, pertussis, hepatitis B virus, Haemophilus influenzae B, etc.. Or it can be
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What is a vaccine?
A vaccine is a biological product. The purpose is to develop protection against infectious diseases;
irreversible immunological reaction; in healthy persons (prophylactic vaccines are given to healthy
persons); and in large populations. The composition is a microbial component (an antigen), adjuvants
(to help to get a good immune response) and stabilisators (to keep the vaccine stable).
Difference between drugs and vaccines
Drug Vaccine
Purpose Treatment of disease Prevention of (infectious) disease
Target population Sick persons Healthy persons
Level of interaction General interaction with the body Specific interaction with the immune system
Means Corrects what went wrong Enhances protective capacity
Immune system Prevent immunological reaction Immunological reaction wanted
Adverse events Sometimes Often local, seldom serious
Dose Individual dosing Dose defined per age group
Advantage Personal cure Personal protection and group protection
The adverse events after a vaccine is often local. For example: your arm will be stiff after the tetanus
vaccine. You are not really sick or ill from the adverse events.
Why develop vaccines?
Vaccines have saved millions of lives. Annually 6 million deaths are prevented. Eradication of
smallpox, so 350 million new victims were identified and 40 million deaths were avoided. What is the
return on investment? For every dollar invested, the return on investment is 40 dollars. However,
evidence shows that effect of vaccines stretches beyond prevention of illness and death!
Vaccine types
There are different vaccine types dependent on the antigen type. The type vaccine influences how
the vaccine is used (target population, etc.), the storage and the administration.
Vaccine types – Whole pathogen vaccines
The oldest form of vaccines are the whole pathogen vaccines. In these types, you use a whole
pathogen (bacterium or virus) and you make a vaccine from this. This can be an inactivated vaccine
or a live-attenuated vaccine. In the inactivated vaccines, the whole bacteria or viruses are inactivated
(by using heat or chemical components). So, there will be no replication of the pathogen. This means
that there will be no disease (also not for immune-compromised people) and not always a strong or
long-lasting immune response. This is a very safe type of disease! The immune response is not that
strong, because the virus is not replicating. The disadvantages are:
May not always induce an immune response at first dose
Response may not be long-lived, requiring several doses of vaccine
So, the inactivated whole pathogen vaccines have a less strong immune response compared to live
vaccines. The advantages are:
Have no live components, so no risk of inducing the disease
Safer and more stable than LAVs
These kind of vaccines have an excellent stability profile. Examples of these kind of vaccines are the
SARS-CoV-2 (Sinovac, Sinopharm), the polio vaccine (inactivated, Salk) or the hepatitis A virus
vaccine. Poliomyelitis is an inactivated polio vaccine by Jonas Salk. It consists of a mixture of three
polioviruses (serotype 1-3). It is produced from wild-type poliovirus strains of each serotype and
inactivated with formalin. It is developed in the 1950s and it can be used in combination with other
vaccines: diphtheria, tetanus, pertussis, hepatitis B virus, Haemophilus influenzae B, etc.. Or it can be
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