6D ❚ WEDNESDAY, MARCH 18, 2020 ❚ USA TODAY NEWS
Memory cells
3) These antibodies attach to antigens on the pathogens and prevent
pathogens from invading other cells. Antibodies signal other white
blood cells, which kill and remove the pathogens.
²
Z
t
²
o
billions of copies, and become a health threat.
̈l
Virus
l
1) When pathogens invade and
shapes. The pathogens have
antigens, special proteins that
̈
2) Some COVID-19
respond to the
infection with an
overreaction that
safe variation of a
pathogen, that
mimics an infection.
̈
²
like a real threat.
How vaccines help your
immune system
How vaccines are created
~z}np~lzol~onp{t
ytltosznon{
oss~
ª
«o
o}~
and senior fellow at the Freeman Spogli
tt~ª
̈«
{ ̈
[
²
white
blood cells
ones called lymphocytes that
antibodies.
qol
laboratories and tested on animals before clinical trials with
ªn«otx
ª
«t
²
methods to administer it.
ªt
«oms
~lzol
² ̈
1) l
3)²
added.
z
DNA and
RNA
trials so far, these vaccines
are based on a bit of the
}}ylZ
vaccines can be developed
than conventional vaccines.
5)
2) ²
~
cells are different, the changed
l
s
p
%
A
Phase I:
Phase 2:
Time Number of test subjects
Several months Twenty to 100
Phase 3:
Several hundred
300 to 3,000
= 1 month
C.n
B.
RNA into the cell
A.
Infected attaches to cell
host cell
Antibody
White blood cell
Bacteria
Antibodies
attach to
antigens
killing
8
Chicken embryo
1— Not
to scale
Adjuvant
Heat
Formaldehyde
Vaccine clinical tests take months
Why a coronavirus vaccine is more than
a year away, despite medical
researchers’ progress
4)
t²
Z
as pathogensviruses and
bacteria.