Biology Now, 2e

22 ■ CHAPTER 02 Evaluating Scientific Claims

SCIENCE

Anna Eaton was, at the time of her research into

vaccines, a high school and community college

science teacher in Cleveland Heights, Ohio.

ANNA EATON

contact with the infectious organism, a vacci-

nated individual’s immune system remembers

the inactivated organism from the vaccine and

is already armed and bristling. The inactivated

organism from the vaccine cannot cause disease

because it was made harmless by the process of

creating the vaccine. The vaccine itself cannot

cause disease because it is not a functional infec-

tious organism and therefore cannot replicate.

Over the past 200 years, scientists have

developed vaccines to protect against dozens

of pathogens, starting with the smallpox virus.

In England in 1796, Dr. Edward Jenner first

vaccinated his gardener’s 8-year-old son against

smallpox using the cowpox virus, because it

was known that individuals who had previ-

ously suffered cowpox were immune to small-

pox. Jenner’s breakthrough ultimately led to

a worldwide smallpox vaccination campaign,

which was so successful that in 1980 the disease

was officially declared eradicated by the World

Health Organization. Vaccines have also been

developed for the Tic Tac–shaped bacteria that

cause the upper respiratory infection diphtheria,

the round and highly contagious rotavirus that

causes vomiting and diarrhea, the tiny airborne

bacteria that cause pertussis (also known as

whooping cough), and many more pathogens.

Before vaccines, children died in large numbers

from smallpox, diphtheria, whooping cough,

polio, and many other diseases (Figure 2.2). The

infectious pathogens that cause those diseases

still exist today in our environment, but because

vaccines protect people, we almost never see

those infections. Today, the Centers for Disease

Control and Prevention (CDC), the public health

branch of the U.S. government, recommends

that children receive 10 vaccines, given over a

total of 24 doses, between birth and 15 months of

age. Additional vaccinations are recommended

between the ages of 18 months and 18 years,

including the annual influenza (“flu”) vaccine,

also recommended for all adults each year

(see “Flu Shot” on page 24).

Eaton, pregnant with her first baby, was a

microbiologist by training. She worked at the

Cleveland Clinic in Ohio, an academic medical

center, before moving on to teach high school

biology and chemistry, as well as bioscience

manufacturing at a local community college.

Some of her friends were also scientists, and

one pregnant friend adamantly commented, “Of

course we’re going to vaccinate. We’re scientists.”

Vaccine Vaccine Antibodies

Disease

organisms Antibodies

When the individual is

exposed to the virus after

vaccination, the new

antibodies are primed to

attack the invader.

The vaccine stimulates the

immune system to produce

antibodies (in green) that

recognize the virus.

A vaccine with a harmless
form of a virus (or other
organism) is injected under
the skin.

Figure 2.1

How vaccines work

A vaccine trains the body’s immune system to fight infection.

Q1: Describe in one sentence how a vaccine creates immunity to a virus.

Q2: Why is it impossible to become infected with a virus from a

vaccine composed of viral proteins?

Q3: Natural immunity occurs without a vaccine, just by exposure to

a particular stimulus, like the chicken pox virus. Explain why people

don’t get chicken pox twice.

I

n 2009, Anna Eaton discovered she was

pregnant. Several of her friends were also

expecting or had recently had children, so

the friends’ afternoon chats were soon about all

things baby: nursery colors, pediatricians, car

seats. Every once in a while, however, one of the

mothers broached a subject far more contentious

than strollers and baby carriers. One of their hot

topics of discussion became vaccination.

Vaccination is the injection of material—

typically an inactivated and harmless infectious

organism or parts of such an organism (e.g., a

single protein)—that stimulates the immune

system to protect against future exposure to that

pathogen (Figure 2.1). When the body’s immune

system is exposed to a vaccine, it recognizes the

inactivated organism (or its parts) as an invader

and mounts an attack against it. Upon later