Biology Now, 2e

A Critical Choice ■ 23

But Eaton was not so confident. She had seen

media stories suggesting that vaccines might cause

autism spectrum disorders, and when she searched

online, she read scary accounts from parents who

had had a child vaccinated and then watched as

their child developed autism. “I’m on message

forums, encountering a hundred different moms

with stories,” recalls Eaton. “It was frightening.”

Stories and anecdotes are powerful. They can

change how we feel or think about a subject. But

anecdotal evidence is not scientific evidence.

Anecdotes are not representative of collected

data or collected scientific observations, and

therefore they cannot reliably give us the big

picture of a subject or phenomenon. Scientific

evidence can.

Eaton’s scientist friend said there were data

backing the safety of vaccines, but Eaton had not

seen those data and wasn’t about to inject her

new baby girl with something she knew noth-

ing about. “Feelings of distrust are in all of us,

and possibly the strongest in a new mother,” says

Eaton. “Even though she was a friend of mine, it

was still not enough for me to just go in the office

and have my daughter vaccinated.”

True or False?

The statement that vaccines cause autism, or

the opposite statement that vaccines are safe,

is a scientific claim, a statement about how the

Diphtheria

1920–22: 13,191 (7.5%)

2000–13: 0 (0%)

Polio

1950–53: 8,050 (9%)

2000–13: 0 (0%)

Pertussis

1922–25: 7,363 (5%)

2000–13: 17 (0.1%)

Smallpox

1600s: 70% Native Americans

1721: 844 (14%) Bostonians

2000–13: 0 (0%) U.S.

Tetanus

1922–26: 1,182 (90%)

2000–13: 4 (14%)

Figure 2.2

Vaccines save lives

The numbers in each box represent each disease’s average annual number of deaths and percent

mortality rate in the United States during prevaccination periods (for example, 1950–53 for polio) and

the postvaccination twenty-first century.

Q1: Before vaccinations, which diseases had the highest and lowest mortality rates? What are

these mortality rates?

Q2: After vaccinations, which diseases have the highest and lowest mortality rates? What are

these mortality rates?

Q3: If there were a sudden outbreak of pertussis at a university where pertussis vaccinations

were not required and no one was protected, how many students would die? What is the

probability or chance that you would die if infected?