Useful information

What is a vaccine in the first place?


Vaccination against new COVID infections has begun in Japan. There are many people who
are interested in it.
What is a vaccine in the first place?
Let me explain it to you from the basics.

What is a vaccine in the first place?

A vaccine is an attenuated pathogen (virus, bacterium, etc.) that causes an infectious
Vaccination creates immunity in the body, and even if it is exposed to the pathogen that
causes the infection, it makes it harder to catch the infection. Even if it is caught, the
symptoms will be less severe.

There are various types of vaccines

Even when you say “vaccine” as a single word, there are actually several types.
● Live vaccine
As the name implies, it is a vaccine that contains live viruses and bacteria.
However, if the pathogen is left as it is, the side reaction will become stronger. Therefore, it is
made from raw materials that are less virulent and less pathogenic.
However, even though it is attenuated, it is still alive, so viruses and bacteria multiply in the
body, which increases immunity.
Live vaccines include measles-rubella mixed (MR) vaccine, varicella vaccine, BCG, and
mumps vaccine.
● Inactivated vaccine
A part of the dead pathogen is inoculated as a vaccine. It is made using only the ingredients
necessary to create immunity, eliminating the infectivity and toxicity of viruses and bacteria.
The immunity produced is weaker than with natural infections and live vaccines, so some
may require multiple doses.
In addition to influenza vaccine, Japanese encephalitis and three-in-one including whooping
cough, diphtheria and tetanus are vaccines of this type.
● Recombinant protein vaccine
A part of viral and bacterial proteins are artificially produced using genetically modified
By artificially creating and administering a protein that serves as a marker for attack,
antibodies that attack pathogens are produced in the body.
● Messenger RNA vaccine
Messenger RNA is a blueprint for making proteins.
The messenger RNA vaccine is based on the blueprint (messenger RNA) for producing the
protein of the pathogen.
By administering artificially made messenger RNA, a specific protein is made in the body,
and immunity (via antibodies) against the pathogen is made.
● Viral vector vaccine
A “vector” is a carrier. The gene that makes the protein of the pathogen is incorporated into
another harmless virus, and the virus is administered into the body.
In other words, it uses a harmless virus as a “carrier” to deliver genetic information.
Then, a specific protein is produced in the body and an antibody is produced, which is the
same as the messenger RNA vaccine.
● DNA vaccine
An artificially created DNA that is inoculated as a vaccine.
The administered DNA enters the nucleus inside the cells of the body to produce messenger
RNA, which produces specific proteins, which in turn produce antibodies.

What is the new corona vaccine?

The vaccines that have been mainly used so far, such as influenza, rubella, and chickenpox,
have been live vaccines or inactivated vaccines. However, these conventional vaccines
require the step of culturing and multiplying the pathogen itself, which is very time
Therefore, for new COVID infections, different types of vaccines from conventional vaccines,
that is, messenger RNA vaccines, viral vector vaccines, and DNA vaccines, which are also
called “gene vaccines,” have been developed.
Currently, the vaccines by Pfizer, Moderna, and AstraZeneca that the Japanese government
has contracted with are messenger RNA vaccines by Pfizer and Moderna, and viral vector
vaccines by AstraZeneca.
◎ Reference
Ministry of Health, Labor and Welfare “Q & A about the new COVID vaccine”
NHK “Special Site New COVID” Vaccine Q & A