Vaccines and Immunisation

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Vaccines and Immunisation

• Medical Microbiology SBM 2044

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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

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Figure 1. Reported diphtheria cases in the Soviet
Union and the Newly Independent States,
19201996.
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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.
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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

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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

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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

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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

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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

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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

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Malaysian Immunisation Schedule
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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
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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

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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.

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Intussuspection
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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
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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 gt 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.

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