The purpose of a vaccine is to mimic an infection, activating the body’s immune response, but without
causing the illness. Conventional vaccines usually contain a weakened or inactivated virus;
or a piece of a viral protein, called an antigen. These viral elements do not cause disease,
but they trick the immune system into thinking that an infection has occurred so that it responds
by producing antibodies against the virus. RNA vaccines are a new generation of vaccines.
Instead of a protein antigen, they contain mRNA, meaning messenger RNA. As its name suggests,
mRNA is basically a messenger, carrying genetic message from DNA to protein. In order to function,
a human cell needs to constantly produce proteins based on genetic information in its DNA.
Because DNA is located in the nucleus of the cell, and protein synthesis occurs in the cytoplasm,
an intermediate molecule is required to transmit the information. mRNA copies
the information from DNA and brings it to the cytoplasm, where it is translated into protein.
mRNA consists of 4 basic building blocks called A, U, C and G. The information it carries is the
sequence of these letters. RNA vaccines contain mRNA strands that have the information for
making the viral antigen, usually a viral spike protein. Once inside the body’s cells, the mRNA is
translated into protein, the antigen, by the same process the cells use to make their own proteins.
The antigen is then displayed on the cell surface where it is recognized by the immune system.
From here, the sequence of events is similar to that of a conventional vaccine.
RNA vaccines are easier and safer to produce than conventional vaccines. Conventional
vaccines typically require growing large amounts of infectious viruses, usually in chicken eggs,
and then inactivating them. Vaccines produced this way are at risks of being contaminated with
LIVE viruses and allergens from egg culture. Such risks do NOT exist with RNA vaccines because mRNA
molecules can be synthesized in a CELL-FREE system using a DNA template that contains information
for making the viral protein. The mRNA is made from the same building blocks as natural mRNA,
so it has the same chemical composition as natural mRNA. The relative simplicity of the production
process makes it easier to standardize and scale, enabling rapid responses to emerging pandemics.
In case the virus MUTATES, it’s also simple to change the mRNA sequence to match the mutation.
RNA vaccines do NOT change your DNA. This is because in order to do so,
the mRNA must convert into DNA, enter the nucleus, and integrate into the cell’s DNA.
This is a complex multiple-step process requiring action of several enzymes that the cell does
NOT have. Instead, the cell has plenty of enzymes that can readily destroy the mRNA,
so the mRNA is usually degraded after the protein is made.
When enough people in a community are vaccinated, the whole community,
including the individuals that were not vaccinated, is protected against the disease.
This phenomenon is known as herd immunity. Herd immunity is possible because a pathogen cannot
spread without a sufficient number of vulnerable hosts. An analogy is the spread of wildfires.
A wildfire only spreads where there is vegetation, or fuel, for it to burn; it would stop at a river,
or a large open space. These are called firebreaks. Vaccinated individuals
essentially serve as firebreaks, preventing spread of infections caused by pathogens. Herd
immunity is important because not everyone can be vaccinated. Often, the very young,
very old, and immunocompromised people must rely on vaccinated individuals to stop disease
outbreaks. To note, however, that the number of vaccinated individuals must be great enough
for community protection to occur, just like a firebreak must be large enough to stop a fire.