Page 21 - Science Focus (issue20)

does not normally propagate for more than several
generations (scientifically termed serial passage), could
Vaccine Development weaken their virulence to the original host [3]. Through

this method, weakened viral strains were collected
and tested on dogs. After they successfully induced
immunity in dogs, Dr. Pasteur tested the same strains on
疫苗研究的發展 a boy who was bitten by a rabid dog. The boy did not
show rabies symptoms.

Dr. Pasteur’s work shows that weakened pathogens
By Paolo Miguel Magallanes Mallorca
may induce immunity against the disease they cause.
This treatment was also named vaccination, which was Types of vaccine summarized:
originally referring to only smallpox, to honor Dr. Jenner’s 1. First-generation vaccine = whole pathogen (live-
Vaccines! Everyone is talking about it lately. We may In 1796, English physician Dr. Edward Jenner proved previous work [3]. attenuated, inactivated)
see them as the way out of this dreadful pandemic this observation by inoculating an eight-year-old 2. Second-generation vaccine = pathogen pieces
that made 2020 a mess. The good news is that some boy with cowpox. The boy only developed fever Modern Vaccine Development (subunit, recombinant)
COVID-19 vaccines are approved and now being and minor symptoms. After his sickness subsided, the 3. Third-generation vaccine = DNA based; mRNA
distributed to billions of people on this planet. With the boy was exposed to smallpox samples but did not Breakthroughs in microbiology and molecular based
vaccines making headlines, have you ever wondered developed the disease. After publishing the results biology in the 20th century drove the development of
where and how do vaccines originate? of the experiments, Dr. Jenner called this procedure more vaccines. Not only there were vaccines available
“vaccination” (derived from the latin word vacca, for more diseases, but there were new methods of The Future of Vaccine Research
meaning cow) and it became more popular than creating vaccines and new types of vaccines as well.
"Vaccination” Before Dr. Edward Jenner variolation [2]. Countries in Europe began to enforce Looking back at how vaccines developed,
It was discovered that pathogens carefully killed
The earliest sign of “vaccination” was documented vaccination and saw significant decline in mortality by heat or chemical treatment can induce immunity, we have come a long way in protecting people
from deadly diseases. In 1980, the W.H.O. declared
in ancient China and India, in the 10th Century [1]. rate [1]. creating inactivated vaccines. The first successful smallpox’s eradication, the complete removal of a
The idea was to collect smallpox samples from blisters inactivated vaccines were created in the 1890s against disease from the human population. More diseases
of a sick individual and inoculating minute amounts Dr. Louis Pasteur: The Father of Immunology typhoid fever and plague. This technique was expanded like malaria and polio may face the same fate in
on healthy individuals. This practice wasn’t called to viruses as well, and by 1936, a vaccine for influenza the future. We have even managed to create a
vaccination but “variolation” (after the smallpox virus While Dr. Louis Pasteur is well known for was invented [4]. vaccine against COVID-19 within a short period
Variola major). It spread across some countries in Asia pasteurization, a method to reduce the load of of time. As more vaccines become available and
and Africa, eventually reaching Britain and other microbial pathogens in food by heat, little attention Inactivated vaccines and live-attenuated vaccines as more research is done, the containment or the
parts of Europe in 1721 [2]. While it was quite effective is given to his other contribution: live-attenuated are referred to as first-generation vaccines. The second- eradication of certain deadly diseases is now a
at protecting people from smallpox and controlling vaccines. Inspired by Dr. Jenner’s works, he suggested generation vaccines are subunit vaccines. Unlike the possibility, thanks to scientists like Dr. Jenner and Dr.
outbreaks, inoculated individuals still have a small risk of that there can be vaccines for other diseases as well. former generation, which uses whole pathogens, Pasteur.
developing smallpox or other diseases transmitted by subunit vaccines use components of the pathogen
this procedure [2]. In 1877, positing that vaccines could be found that can be targeted by the immune system to develop
for all virulent diseases, Dr. Louis Pasteur attempted immunological memory [4]. With the recent advances
to work on chicken cholera [3], a bacterial disease in genetic engineering, one variant of subunit vaccines
Dr. Edward Jenner: The that was devastating chicken populations. One time uses recombinant DNA technology to mass-produce
Pioneer of Vaccines before going on a holiday, he instructed his assistant these components in other organisms or cells, such as
to inoculate chickens with fresh bacterial samples. yeast, animal cells and insect cells [4].
I n the 170 0 s, some The assistant forgot and upon returning, he inoculated
milkmaids were reported the chickens with samples that had been sitting in the Then is the relatively new, third generation of
t o h a v e i m m u n i t y laboratory for a long time. The inoculated chickens vaccines. Instead of administering patients with whole
a ga i n s t sm a l l p o x . survived, and remained healthy upon exposure to fresh pathogens or their components, genetic materials
This was likely due to samples afterwards. It was later discovered that the old coding for those components in the form of DNA or
prior infection with samples were probably weakened due to prolonged mRNA are used. These genetic materials will be read
cowpox, a disease exposure to oxygen, but could still induce immunity. This by cells as instructions to produce viral components
similar to but milder is the first example of a live-attenuated vaccine. for the immune system to target. Due to the COVID-19
than smal lpox. pandemic, both DNA and mRNA vaccines are
Dr. Pasteur’s accidental discovery of the chicken receiving a lot of attention lately, which are the first
cholera vaccine inspired him to work on other diseases. of their kind to be approved for emergency use in
In 1885, he worked on rabies, a fatal neurological humans. The development of DNA and mRNA vaccines
d i s e a s e i n d o g s a n d was spurred unprecedentedly by the race to develop
humans. It was discovered vaccines against COVID-19. Besides their application in
that growing rabies virus the pandemic, research is being done for the potential
in other hosts like rabbits use of such nucleic-acid based vaccines against
where the microbe cancer and HIV [5].

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