Contents:
Introduction
The benefits of immunization are readily apparent when the number of cases
(in this case, Canadian) are examined before and after the introduction of
certain vaccinations*:
* Taken from: Canadian National Report on Immunization, 1998
Affecting
Disease |
Cases -
Pre-Vaccination |
Introduction
of Vaccine |
Cases -
Post-Vaccination (1998) |
| Smallpox |
Hundreds of thousands worldwide |
1798; global immunization began in 1967 |
0 |
| Diptheria |
9,000 in 1924 |
1926 |
1 |
| Whooping Cough |
17,000+ annually |
1943 |
7519 |
| Poliomyelitis |
11,000 between 1949 and 1954 |
1955, 1962 |
0 |
| Measles |
300,000 - 400,000 annually |
1963 |
12 |
| Mumps |
30,000 in 1940's and 1950's |
1969 |
110 |
Table of Vaccines
|
Cholera Vaccine: While cholera is not currently a life-threatening
disease in Canada and the U.S., it is still prevalent in parts of the
Middle East, Latin America and Asia. A vaccine is available to protect
travelers to these parts of the world.
Diphtheria Vaccine (DPT vaccine): This is usually given to children combined with tetanus and
pertussis (whooping cough) vaccines. Adults generally receive them every
7-10 years.
Haemophilus B Vaccine: Children can be protected against the haemophilus Type B bacterium with a
vaccine usually given at 2 years of age. This vaccine is particularly
recommended for children who attend day-care centers.
Hepatitis B Vaccine: Two
vaccines are available for people who are at risk of acquiring hepatitis B.
Travelers to a country where hepatitis B is prevalent, health care workers
exposed to the hepatitis B virus, and other high-risk individuals have the
option of protecting themselves against this disease due to the availability
of these vaccines.
Influenza Vaccine: While
vaccination against influenza is not recommended for the public at large,
some people, such as the elderly, are at risk of serious illness if they
contract influenza.
Measles Vaccine (MMR Vaccine): A live weakened measles vaccine is routinely given to infants,
usually in combination with mumps and rubella vaccines (MMR vaccine).
Meningococcal Meningitis:
While meningitis is relatively uncommon in North America and Europe, the
disease is prevalent in regions of Africa and South America. Several
vaccines are available to protect travelers to these areas of the world.
Mumps Vaccine (MMR Vaccine):
Mumps vaccine is given to children in one dose, usually in combination with
measles and rubella vaccines (MMR vaccine).
|
Plague Vaccine: Plague is not a disease found today in the United States, but a
vaccine is available to protect travelers to areas of the world where the
disease is still prevalent.
Pneumococcal Pneumonia Vaccine: While this vaccine is not recommended for the general population,
elderly people and other high-risk individuals often choose to become
vaccinated.
Polio Vaccine: Infants
usually receive a live polio vaccine orally at the same time as the DPT
vaccine. Because of the polio vaccine, very few cases of this deadly disease
are now reported.
Rabies Vaccine: While
protection against rabies is not necessary for the general population, a
vaccine is available for those who travel to or live in areas of the world
where rabies is common in domestic animals--areas such as India and parts of
South America. Veterinarians also are routinely inoculated against rabies.
Rubella Vaccine (MMR Vaccine): This vaccine (also called the Red Measles vaccine) is usually given
to infants, in combination with measles and mumps vaccines (MMR vaccine).
Although rubella is not a life-threatening disease, if a woman is exposed to
it while she is pregnant, her child may be born with severe birth defects.
Tetanus Vaccine: Tetanus
vaccination is usually given to children as a series of shots and is
completed by the time they enter school. It is recommended that adults
receive a tetanus/diphtheria booster every 7-10 years.
Typhoid Vaccine: While
typhoid is uncommon in the west, it is found in many developing countries. A
killed vaccine is available to protect travelers to these countries.
Yellow Fever Vaccine: Yellow
fever is not a threat to the population of North America, but it is
widespread in certain areas of Africa and South America. A live virus
vaccine is available to protect travelers to these countries.
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Early Vaccines
In the 1800's, outbreaks and epidemics of plague, cholera, smallpox,
typhoid fever, tuberculosis, scarlet fever
and other dread diseases ravaged entire populations, as they had for centuries.
In the 18th century, the average human
life expectancy was 31 years. One of the worst killers at this time was
smallpox, which killed one out of every ten children under the
age of four. In 1796, Edward Jenner, an English country doctor, developed a
vaccine against this dread disease that became a model for all later vaccines.
Dr. Jenner had observed that dairymaids who suffered from a mild infection
called cowpox seemed to be protected from smallpox. Based on
this observation, he inoculated people with cowpox and found that it was
possible to give them the same immunity as the dairymaids.
As a result of Jenner's work, inoculation
campaigns against smallpox were launched in North America and Europe. As a
result of refinements which made possible the development of a more stable dried
vaccine, in 1967 the World Health Organization (WHO) launched a global campaign
to eliminate smallpox. Today smallpox has been eradicated throughout the
world.
In the mid-19th century, French chemist Louis
Pasteur developed a method for controlling the growth of bacteria, a process
which became known in the dairy business as "pasteurization."
Pasteur's achievement led to the realization that microorganisms can cause
disease, a fact we take for granted in the 20th century.
Pasteur became interested in chicken
cholera in the mid-19th century. At one point during his study, he
infected a group of chickens with an old culture of cholera bacteria, which
caused them to develop only a mild case of the disease. When he later infected
them with fresh cholera germs, the chickens remained healthy, and Pasteur
concluded that they were protected from the disease.
Based on this success, he turned his interest to
the study of anthrax in cows. Producing a mixture of dead and
weakened anthrax bacteria, he successfully protected a group of cows against
this deadly disease. He called this mixture a vaccine, after the Latin "vacca"
meaning "cow." Following the same formula, in 1885 Pasteur next
developed a vaccine for rabies in animals, which he eventually proved was
effective for humans as well.
Vaccination against diphtheria
was made possible in the late 19th century due to work with guinea pigs.
Biomedical researchers extracted diphtheria toxin from a broth in which they
grew the bacterium. They proved that this toxin was the cause of diphtheria by
testing it in guinea pigs, sheep and other animals. Working with guinea pigs
infected with diphtheria bacilli, the researchers found a chemical which allowed
some of the animals to survive. Blood samples from these immune guinea pigs were
extracted, and the serum containing the diphtheria antitoxin was injected into
the animals already infected with diphtheria.
Once the antitoxin was proven to help these
animals suffering from diphtheria, guinea pigs (and later horses) were used to
produce the antitoxin for people suffering from the disease. Diphtheria
antitoxin became available for human use in 1895, at a time when the mortality
rate for children with this disease was more than 50%.
|
One Canadian physician who practiced north of Toronto in the last century
recorded in his daybook that one-quarter of all the
children who died in his practice succumbed to Diphtheria. The disease is
now extremely rare. |
These and other early vaccines were breakthroughs
that paved the way for all of the immunizations which we now take for granted.
Animals were instrumental not only in the investigation of the diseases and the
development of vaccines, but in some cases, also in the production of the
vaccine itself. Both animals and people now live longer and healthier
lives as a result of these vaccines.
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