How vaccines work against COVID-19: Science, Simplified

After we've been exposed to an infection,

our immune system remembers the threat

in particular by producing antibodies.

These are proteins that circulate
in the blood and throughout the body.

They quickly recognize and disable
the invader upon contact,

thereby preventing or minimizing illness.

This is why we usually do not get sick
with the same bug twice.

We are immune.

Vaccines mimic this process,

encouraging the immune system to make
antibodies

without us having to go through
the illness.

Some of the leading SARS-CoV-2 vaccine
candidates are

mRNA vaccines

based on incorporating the
genetic blueprint

for the key spike protein on the
virus surface

into a formula that, when injected into
humans,

instructs our own cells to make the spike
protein

In turn, the body then makes antibodies
against the spike protein

and they protect us against
viral infection

This strategy is faster than more
traditional approaches

Which often involve generating weakened or
inactivated forms of a live virus

or making large amounts of the spike
protein

to determine whether they can prompt
an antibody response

Once a potential vaccine is discovered,

a number of checkpoints exist before it
can be administered to people

First, a pre-clinical test, which involves

experiments in a laboratory and with
animals

Scientists must ensure the vaccine
candidate

is not only effective, but also safe

For example, an antibody response to an
imperfect vaccine could,

under extremely rare circumstances

end up increasing the danger of becoming
infected

When the potential vaccine achieves
the necessary pre-clinical results

clinical trials can begin in a small
group of people

As the vaccine candidate advances

it is tested on increasing numbers of
people

with scientists and doctors closely
monitoring

safety, efficacy, and dosing

Upon successful completion of
clinical trials,

the vaccine candidate must be reviewed
and approved

by regulatory agencies

such as the FDA

before large scale manufacturing
and distribution

gets underway

and the licensed vaccine is administered
widely