1. Vaccines and Immunisation
Medical Microbiology SBM 2044

2. Immunisation
Decrease in the incidence of infectious diseases since the middle 19th century due to:
improved sanitation
the development of vaccines
Efficient water supplies and sewage disposal have reduces the transmission of typhoid, cholera, tuberculosis, typhus and plague agents.
Administration of vaccines have successfully eradicate smallpox; live, attenuated vaccines decrease the incidence of polio, measles, rubella, mumps and varicella.
Toxoid vaccines have caused a decline in diphtheria, tetanus and pertussis

3.
Figure 1. Reported diphtheria cases in the Soviet Union and the Newly Independent States, 1920–1996.

4. INACTIVATED VACCINE
ORAL VACCINE
Figure 2. The incidence of paralytic poliomyelitis peaked in the US in 1952 with more than 20,000 cases. Because of the introduction of the killed IPV, or Salk vaccine, in 1954 and the live attenuated OPV, or Sabin vaccine, in 1961, the incidence has decreased to less than 10 cases per year in the US.

5. Is there any drawbacks of vaccinations?
Infectious diseases rising, despite the advances in sanitation and the use of vaccines.
Why?
Vaccines have not been developed for many pathogens, many which are major concerns of health e.g. HIV, respiratory diseases
Institutional public health control measures are difficult
Public concerns of the effectiveness and safety of vaccines

6. Terminology:
Vaccine : an immunizing agent derived from microorganisms, and can be either in the form of live, attenuated microorganisms, killed microorganisms and extracts of microorganisms
Attenuate : to reduce the severity, virulence or vitality
Toxoid :

7. Terminology:
Vaccine : an immunizing agent derived from microorganisms, and can be either in the form of live, attenuated microorganisms, killed microorganisms and extracts of microorganisms
Attenuate : to reduce the severity, virulence or vitality
Toxoid : an inactivated bacterial toxin that has lost its toxic properties but capable of inducing protective antibody

8. Approaches to Immunisation
Vaccinations to prevent infectious diseases have been greatly successful
The benefits include partial or complete protection against infections both for the vaccinated individuals, and for society as a whole
Benefits to society include the establishment and preservation of herd immunity, prevention of outbreaks and decrease in health care-related costs
Herd immunity:  When most of the population is immune from a disease.  (With herd immunity, the disease does not have enough susceptible hosts to establish an epidemic.  In other words, controlling a disease does not necessarily require that everyone be immune to it.)

9. Is vaccine safe? No vaccine is completely safe or effective.
Immunisation practices must weigh the scientific evidence of the benefits for each person and for society against the potential costs and risks of the vaccination program

10. Strategies for immunisation
The choice of treating infectious diseases depends on:
The type of microorganisms
The age of the host
The time frame of contact between the host and the pathogen
Active immunisation – administration a microorganism, or a modified product of that microorganism to evoke an immunologic response; useful for preexposure control
Passive immunisation – administration of exogenously produced or preformed antibodies for the amelioration or prevention of infectious diseases; useful for postexposure control

11. Malaysian Immunisation Schedule

12. Vaccines Major types of vaccines: Characteristics Examples
1.Attenuated whole-agent vaccines
Living but weakened viruses
Sabin polio vaccine, MMR (measles, mumps and rubella)
2. Inactive whole-agent vaccines
Dead microbes
Rabies, influenza, Salk polio vaccine, cholera
3. Toxoids
Inactivated toxins
Tetanus and diphtheria taxoids
4. Subunit vaccines (including recombinant vaccines, produced by genetic engineering)
Use only the antigenic part of microbes; most safe and having least side-effects
Hepatitis B vaccine

13. Live vs. Killed vaccines
Vaccines are designed to stimulate antibody or cell-mediated immune responses directed against critical virulence factors of the organism
e.g. capsular polysaccharides of pneumococci, surface glycoprotein of hepatitis B virus and the haemagglutinin and neurominidase proteins of influenza virus
Immunity generated by a killed vaccine is not as effective nor long lasting as immunity stimulated by a live, attenuated vaccine

14. Live, attenuated vaccine
Cold-adapted influenza vaccine containing a weakened form of live influenza virus, and is administered by nasal spray (c.f. injection). Cold-adapted indicates that the virus can grow in the nose and throat but not in the lower resp t. where the temp is higher.
There is a risk that attenuated vaccine strain could revert to a more virulent strain in a susceptible host. E.g. vaccine-acquired paralytic poliomyelitis (VAPP) after millions of live polio vaccine was administered.
Live, attenuated rotavirus vaccine was found to be associated with an increased rate of intussuspection.

15. Intussuspection

16. Types of Immune Response
Type of vaccine
Immune response
Live, attenuated organisms e.g. poliovirus
B cells, CD8+ and CD4+ T cells
Inactivated organisms (rabies, poliovirus), protein antigens (diphteria, tetanus, pertussis) and capsular polysaccharides plus a protein carrier (Haemophilus influenzae type B polysaccharide linked to a bacterial toxoid)
B cells and CD4+ T cells

17. Age of Immunisation
Which serum antibody does the newborns directly received from their mothers?
Which secretory antibody is available in breast milk?
Humoral immunity responds well to protein antigens like DPT when given at 2 months of age, but not to certain polysaccharide antigens
Hepatitis B vaccine is immunogenic when given at birth
Live, attenuated viruses like MMR, are given after the 1st year of life because of the potential interference of maternally derived antibodies
The elderly > 65 years of age, have reduced capability to mount a primary antibody response to some antigens such as influenza virus and pneumococcus vaccine but able to mount secondary responses.
Other factors that may affect immunisation: nutritional status, presence of underlying disease and age.

18. Malaysian Immunisation
Recommended Immunisation Schedule for Infants and Children Not Immunised at the Recommended Time

19. Immunization program for the risk groups
Special populations
Vaccine
Susceptible health-care personnel
Hepatitis B, measles, mumps, influenza, varicella, rubella, (BCG)
Veterinarians, animal handlers and animal bite victims
Rabies
Handlers of imported animal hides, furs, bonemeal
Anthrax
Food handlers
Typhoid
Military personnel
Meningococcus, yellow fever, anthrax
Pregnant women
Hepatitis B vaccine, tetanus toxoid, influenza vaccine
People with sickle cell disease, splenectomized patients
Pneumococcal, meningococcal, Haemophilus influenzae vaccine
Travellers to certain areas
Meningococcus, yellow fever, cholera, typhoid fever, plague, Japanese B encephalitis, polio