Transcript Vaccination

Vaccination
Vocabulary Check
• Vaccination: conferring immunity to a disease by
injecting an antigen (of attenuated
microorganisms or inactivated component) so
that the body acquires antibodies prior to
potential infection
• Immunization: the injection of a specific antigen,
derived from a pathogen, to confer immunity
against a disease
• Inoculation: to introduce a microorganism into an
environment suitable for its growth
• Attenuated: weakened, with diminished or no
ability to cause disease
History of Vaccines
• Although it had long been recognized that those
who had a disease once rarely contracted the
same disease again, the process of immunization
was not widely introduced until 1796 by Edward
Jenner.
• Jenner realized that milkmaids who contracted
cowpox, a mild disease, rarely got smallpox, a
much deadlier disease.
• To test his hypothesis, Jenner inoculated an 8
year old boy with fluid extracted from a cowpox
pustule of an infected individual. The boy got a
mild infection, but when he was later exposed to
smallpox, he remained healthy.
History of Vaccines
• Louis Pasteur later noticed a similar
phenomenon with chicken cholera bacterium.
Chickens which were inoculated with aged
bacteria only got a mild version of the disease,
and when inoculated again with fresh
bacteria, they were immune. The bacteria had
become attenuated.
History of Vaccines
• Since this discovery, many vaccines have been
produced. Some of the diseases which are
vaccine-preventable are:
– Hepatitis A & B
– Influenza
– Measles
– Rabies
– Tuberculosis
How Vaccines Work
• Vaccines are injected or administered by
mouth. Very new vaccines are available as
nasal sprays.
• Vaccines contain antigens to a disease which
are inactivated or attenuated, and which
stimulate an individual’s immune system to
produce antibodies.
How Vaccines Work
• Vaccines can be manufactured in several ways:
– from dead or attenuated bacteria
– from inactivated viruses
– from purified polysaccharides from bacterial cell
walls
– from inactivated toxins
– from recombinant DNA produced by genetic
engineering
How Vaccines Work
• Antibodies produced in response attack the
vaccine antigen, and memory cells persist in
the body.
• It is these memory cells that will later prevent
infection by the same antigen.
• This is termed active artificial immunity.
Primary vs. Secondary Response
Greatest Vaccine Success Story
• Eradication of Smallpox
– virus enters throat & respiratory tract,
targeting phagocytes and blood cells
– flu-like symptoms, leading to lesions, rash,
scabs, severe scarring (if individual survives)
– mortality rate around 30%
– transmitted by direct contact with infected
individual
Greatest Vaccine Success Story
– in 1950s there were
approximately 50 million cases
per year
– in 1967, World Health
Organization (WHO) began the
Intensified Smallpox Eradication
Programme
– strategy: mass vaccinations,
followed by intensive
surveillance
– 1979 declared smallpox
eradicated
Vaccine Side Effects
Common side effects:
• fever
• allergies
• minor swelling and pain at injection site
Rare side effects:
• panencephalitis (inflammation of the brain) from
measles vaccine
• mutation of attenuated strain to virulent strain
• brain damage from unknown cause (Whooping
cough vaccine)
Benefits
Complete eradication of
diseases (e.g. Smallpox)
Reduced death rate from
diseases (e.g. measles)
Reduced long term
disabilities (e.g. blindness
in rubella babies)
Dangers
Excessive vaccination may
reduce the effectiveness of
the immune system to
respond to new infections
Vaccine immunity less
effective than natural
immunity (e.g. measles)
Side effects such as
possible autism from MMR
vaccine