two drops of life
“Do Boond zindagi ki” When Amitabh
Bachchan voiced those words, millions of parents in India rushed their kids
below the age of five to the nearest polio booth to get them vaccinated. The
outcome In 2016, WHO declared India a
“polio-free nation” marking its victory
over a twenty year long battle against the crippling disease of poliomyelitis.
Before the advent of vaccines, a person could
become immune to a disease only by getting the disease and with luck, surviving
it. This way of naturally acquired resistance required one to suffer all the
symptoms of an infection, risk the complications, which could be fatal, and
isolate oneself from society to keep a contagious disease from spreading.
Vaccines provide a safer alternative of artificially imparting active immunity
to a person without actually causing the disease or risking its transmission to
Today, diseases like plague, polio, tetanus, typhoid, whooping cough that were once prevalent are
all but forgotten in most parts of the world and much decreased in occurence in
other regions. This achievement in worldwide health has been possible only by
the emergence of vaccination; proven to be the best method of disease
prevention in both safety and cost efficiency.
Vaccination is a means of educating the immune
system to recognize and fight a pathogen effectively, protecting the body from
the infectious disease. It is based on the ability of our immune system to
distinguish between self and non self, and elicit an immune response against
the foreign agent, introduced through vaccine, which it remembers for a long
time. So the next exposure to the same foreign particle triggers a much
stronger immune response that kills the pathogen upon entry and no ailment
Edward Jenner, an English physician, is mostly credited for the development of
vaccination through the inoculation of an eight year old boy with fluid from a
cow pox postule of a milkmaid, resulting in successful immunity against smallpox in
1796. Although Jenner’s contribution was significant, it was
years before Jenner, a farmer in England named Benjamin Jesty
his family with cowpox virus to induce
resistance to smallpox. He
exposed his children to smallpox patients to prove their immunity.
However, as it has been stated by scientist Francis Galton,
“In science credit goes to the man who convinces the world,
not the man to whom the idea first occurs”.
Jenner was able to publish his work and propagate
the idea of vaccination strongly, becoming the pioneer of
The first attempts to induce immunity date back to the fifteenth century, when
the Chinese practised nasal insufflation wherein dried crusts from smallpox
pustules were inhaled up the nostrils to immunize healthy individuals. Smallpox
inoculation or variolation was also practised in Turkey and parts of Africa, in
which fluid from pustules was rubbed into cuts made in the skin of a healthy
person rendering him immune to smallpox.
During the “milder disease” outbreaks in seventeenth century India, pox-laden
blankets were collected and susceptible children were wrapped in them with the
intention of transmitting mild disease.
In the eighteenth century, variolation got introduced to Europe when Reverend
Cotton Mather learnt about it from African slaves and began to promote the
practice from there on. Also in 1718, Lady Mary Wortley Montagu, wife of
ambassador to Turkey, heard about it on arrival in Turkey and got her children
In 1880, Louis Pasteur presented his finding that an old culture of cholera
bacteria administered to chickens rendered them protected against cholera. He
coined the term vaccine ( _vacca_ means “cow” in Latin), in honour of
Jenner’s work, for the attenuated strain he used. He extended the discovery to
other pathogens and came up with vaccines for anthrax and rabies.
The development of vaccination led to the study
and understanding of the immune system, laying the foundation of
immunology as a new field of medical science.
Twentieth century saw the emergence of a number of vaccines against various
diseases. Different types of vaccines exist in use today:
1. Live attenuated
vaccines contain active but weakened microorganisms that are non-virulent.
2. Inactivated vaccines
contain pathogens killed by chemicals or heat.
3. Toxoid vaccines consist
of inactivated exotoxins produced by the organism.
4. Subunit vaccines
contain a protein subunit of the pathogen.
5. Conjugate vaccines have
polysaccharide linked to a protein carrier.
vaccines and recombinant vector vaccines that can deliver antigen encoding
genes and directly activate immune cells are under clinical trials.
The main aim of vaccination is to stimulate the
adaptive immune system without provoking an acute inflammatory response of the
innate immune system which would result in symptoms of the disease. Following injection,
the antigens in the vaccine attract dendritic cells, monocytes and neutrophils
that circulate throughout the body. Elicitation of sufficient signals by the
antigens activates the helper T lymphocytes and cytotoxic T lymphocytes which mediate killing of altered self cells. They further
generate B lymphocytes which mature into
plasma cells and secrete antibodies that bind to and clear the antigens from
the body. Some activated T and B cells become memory cells that remain in the body
and help the system remember the antigen until the next infection to trigger a
more potent response in less time.
vaccination of children is begun at birth and a schedule recommended by WHO is
followed upto 18 years of age. International travellers are also routinely
vaccinated for diseases endemic to their
A milestone in vaccinology was witnessed with the elimination of small pox from
the world in 1977. While the success of a similar drive against polio is still
awaited, vaccination is posed by challenges of resistance, in certain areas,
based on rumours of association of vaccines with sterility, autism. Though
unfounded, these misconceptions need to be overcome for successful immunization
of the masses.
Vaccination saves 6 million lives every year. Vaccination is not about
protecting one person, it’s about protecting the entire community- it is public
health in the truest sense.
The success of smallpox eradication has made worldwide immunization to various
diseases a realistic proposal. All we require is to develop better, safer,
cheaper, easier to administer vaccines.
Kuby Immunology (2007)
6th ed., Kindt, T.L., Goldsby, R.A. and Osborne, B.A., W.H Freeman and Company
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KA. The myth of the medical breakthrough: smallpox, vaccination, and Jenner
reconsidered. Int J Infect Dis. 1998;3:54–60
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