Name____________________________________________________________________________ Period_________
Vaccines, Viruses & Bad Science
Vaccines and Herd Immunity
Hailed as one of the most important medical advances
of the 20th century, vaccines have eradicated viruses
like polio, smallpox, and diphtheria from the United
States and continue to save millions of lives all over the
world. How exactly do they work? Vaccines contain a
few micrograms of the actual virus you are trying to
immunize against. For example, the measles vaccine
contains parts of actual measles virus cells. These
small doses stimulate your immune system to create
antibodies against the virus, without actually causing
the disease. The antibodies will go into action to
defend your body if you happen to come into contact
with the virus later in life.
As more and more people get vaccinated in a given
area, the diseases lose the opportunity to spread. This
is what scientists refer to as “herd immunity.” Usually
about 85-95% of the population needs to be naturally
immune or vaccinated against a virus in order to
prevent outbreaks. This is especially important for
individuals who are ineligible to receive vaccinations –
infants, pregnant women, and people with
immunodeficiency – as they rely on this containment of
the virus to keep them safe. Rhett, a child from
California who cannot be vaccinated because his
immune system is compromised, relies on everyone
around him for protection from these communicable
diseases. That is how herd immunity works.
Analysis Questions
1. Explain what a vaccination is and how it works:
2. Explain the concept of “herd immunity” in your own words:
Anti-Vaccination Movement
Despite a growing scientific consensus surrounding the link
between vaccinations and immunity, the “Anti-Vaccination
Movement” is gaining momentum at an alarming rate. This vocal
minority claims that vaccines can cause autism and other
devastating side effects. Michelle Bachman, a presidential nominee
in the 2012 election even went as far as to claim that the HPV
vaccine causes mental retardation in girls. Scary, right? Let’s take
a look at some of the scientific evidence behind these claims.
In 1998, Andrew Wakefield published a paper in which he claimed
he had discovered a link between the MMR (Measles, Mumps,
Rubella) vaccine and autism. Despite the fact that this was a preliminary study, using only 11 individuals, this story
took off like wildfire. As parents began to question the validity of vaccinations, celebrities like Jenny McCarthy and
Jim Carrey furthered the uproar by claiming their own children had been victims of this connection.
Many follow-up studies were performed testing the autism-MMR vaccine correlation, making it increasingly clear
that there was no link between MMR and autism. For example, a study in the British Medical Journal found that
autism rates continued to climb in areas where MMR vaccination rates were not increasing (Taylor 1999). Other
studies showed no difference in the diagnosis rate of autism either before or after the MMR vaccine was
administered (Honda 2005), or between vaccinated and unvaccinated children (Madsen 2002). Most recently, a
study found that there was no decrease in autism rates following removal of the MMR vaccine (Honda 2005).
Analysis Questions
3. What are the claims of the Anti-vaccination movement?
4. Even if there had been no follow-up studies to Wakefield’s, what is one critical error he makes?
5. What effect might the anti-vaccination movement have on herd immunity in the United States?
Consequences
Outbreaks of diseases like the measles and whooping
cough are on the rise in the United States as more and
more parents choose to not vaccinate their children. In
Marin County, California, 6.5% of school children are not
vaccinated due to the “personal belief exemption,” which
allows parents to send their children to school unvaccinated
against diseases like measles, polio, whooping cough and
more. This may sound like a low number, but when it
comes to herd immunity and containing outbreaks, this is
significant.
The CDC estimates that 164,000 people around the world
will die from measles each year, and it is experiencing quite
a resurgence in the UK. The United States has recently
seen a drastic increase in whooping cough, which causes
around 195,000 deaths per year. The majority of these
deaths occur in impoverished regions with very little access
to vaccines. In the case of developed areas like the US or
UK, they shouldn’t be happening at all.
In 2014, a measles outbreak started in Disney Land, when one unvaccinated woman visited the park. The
outbreak affected 195 individuals who contracted the disease while visiting the park, and brought it back home to
over 11 states. Six of the confirmed cases were of infants under 12 months old, too young to receive the vaccines.
That year, over 667 measles cases were reported in the U.S. – the highest number of cases since measles
eradication was documented in 2000.
Analysis Questions
6. Why do you think measles cases can still spread the United States, even after it had been eradicated?
7. It is often said that getting vaccinated is not about yourself, they’re about everyone else. What do you
think is meant by that?
8. What other information would you like to know before you deciding whether to vaccinate your children?
Correlation and Causation Analysis
The WHO recommends the first dose of the MMR
vaccination be given when the child is between 9 and 12
months old, with the second dose administered 6
months later when the child is between 15 and 18
months old. Autism symptoms usually begin to present
between 18 and 36 months. Although Autism symptoms
and the MMR vaccine happen to occur at the same time
in a child’s life, does not mean that the two are related.
Correlation does not necessarily equal causation. That is
to say, just because these two things happen to occur at
about the same age, does not necessarily mean there is
a link.
Graph 1 is specifically meant to illustrate the point that
correlation, does not equal causation. There is an
extremely high statistical significance (p<0.0001) between
organic food sales and autism diagnoses. Does
this necessarily mean that organic food causes autism?
Probably not.
Graph 1: Autism and Organic Foods?
Graph 2 shows the likelihood of having autism correlated
with several different factors. For example, it shows that
children who had the MMR vaccine were 0.9x more likely
to have Autism. It also shows children who have a
Cerebellar injury (brain injury) at birth are 36x more likely
to be diagnosed with autism.
Analysis Questions
9. Explain in your own words, what is meant by the phrase
“correlation does not necessarily mean causation.”
Graph 2: Correlations with Autism
10. Based on graph 2, what do you think scientific
research money should be spent on to investigate the
true cause of autism?
11. Figure 3 shows the morbidity from several diseases
before and after vaccines were introduced. What
conclusions can you draw?
Graph 3: Vaccines and Morbidity
Vaccines, Viruses & Bad Science KEY
Vaccines and Herd Immunity
Hailed as one of the most important medical advances
of the 20th century, vaccines have eradicated viruses
like polio, smallpox, and diphtheria from the United
States and continue to save millions of lives all over the
world. How exactly do they work? Vaccines contain a
few micrograms of the actual virus you are trying to
immunize against. For example, the measles vaccine
contains parts of actual measles virus cells. These
small doses stimulate your immune system to create
antibodies against the virus, without actually causing
the disease. The antibodies will go into action to
defend your body if you happen to come into contact
with the virus later in life.
As more and more people get vaccinated in a given
area, the diseases lose the opportunity to spread. This
is what scientists refer to as “herd immunity.” Usually
about 85-95% of the population needs to be naturally
immune or vaccinated against a virus in order to
prevent outbreaks. This is especially important for
individuals who are ineligible to receive vaccinations –
infants, pregnant women, and people with
immunodeficiency – as they rely on this containment of
the virus to keep them safe. Rhett, a child from
California who cannot be vaccinated because his
immune system is compromised, relies on everyone
around him for protection from these communicable
diseases. That is how herd immunity works.
Analysis Questions
1. Explain what a vaccination is and how it works:
They contain micrograms of the actual virus to stimulate your immune system to create antibodies against the
virus, without actually causing the disease.
2. Explain the concept of “herd immunity” in your own words:
When about 85% of the population is vaccinated, the virus loses opportunity to spread. This prevents outbreaks
and protects those who cannot be vaccinated.
Anti-Vaccination Movement
Despite a growing scientific consensus surrounding the link
between vaccinations and immunity, the “Anti-Vaccination
Movement” is gaining momentum at an alarming rate. This vocal
minority claims that vaccines can cause autism and other
devastating side effects. Michelle Bachman, a presidential nominee
in the 2012 election even went as far as to claim that the HPV
vaccine causes mental retardation in girls. Scary, right? Let’s take
a look at some of the scientific evidence behind these claims.
In 1998, Andrew Wakefield published a paper in which he claimed
he had discovered a link between the MMR (Measles, Mumps,
Rubella) vaccine and autism. Despite the fact that this was a preliminary study, using only 11 individuals, this story
took off like wildfire. As parents began to question the validity of vaccinations, celebrities like Jenny McCarthy and
Jim Carrey furthered the uproar by claiming their own children had been victims of this connection.
Many follow-up studies were performed testing the autism-MMR vaccine correlation, making it increasingly clear
that there was no link between MMR and autism. For example, a study in the British Medical Journal found that
autism rates continued to climb in areas where MMR vaccination rates were not increasing (Taylor 1999). Other
studies showed no difference in the diagnosis rate of autism either before or after the MMR vaccine was
administered (Honda 2005), or between vaccinated and unvaccinated children (Madsen 2002). Most recently, a
study found that there was no decrease in autism rates following removal of the MMR vaccine (Honda 2005).
Analysis Questions
3. What are the claims of the Anti-vaccination movement?
These vaccines can cause autism, mental retardation and other problems.
4. Even if there had been no follow-up studies to Wakefield’s, what is one critical error he makes?
He only uses 11 individuals, meaning his sample size is way too small.
5. What effect might the anti-vaccination movement have on herd immunity in the United States?
If fewer people decide to get vaccinated, the virus will have many more opportunities to spread. This can greatly
affect herd immunity and individuals who are particularly vulnerable.
Consequences
Outbreaks of diseases like the measles and whooping
cough are on the rise in the United States as more and
more parents choose to not vaccinate their children. In
Marin County, California, 6.5% of school children are not
vaccinated due to the “personal belief exemption,” which
allows parents to send their children to school unvaccinated
against diseases like measles, polio, whooping cough and
more. This may sound like a low number, but when it
comes to herd immunity and containing outbreaks, this is
significant.
The CDC estimates that 164,000 people around the world
will die from measles each year, and it is experiencing quite
a resurgence in the UK. The United States has recently
seen a drastic increase in whooping cough, which causes
around 195,000 deaths per year. The majority of these
deaths occur in impoverished regions with very little access
to vaccines. In the case of developed areas like the US or
UK, they shouldn’t be happening at all.
In 2014, a measles outbreak started in Disney Land, when one unvaccinated woman visited the park. The
outbreak affected 195 individuals who contracted the disease while visiting the park, and brought it back home to
over 11 states. Six of the confirmed cases were of infants under 12 months old, too young to receive the vaccines.
That year, over 667 measles cases were reported in the U.S. – the highest number of cases since measles
eradication was documented in 2000.
Analysis Questions
6. Why do you think measles cases can still spread the United States, even after it had been eradicated?
More and more parents are choosing to not vaccinate their kids. This leaves many more vectors for the
virus to take hold and spread to other unvaccinated individuals.
7. It is often said that getting vaccinated is not about yourself, they’re about everyone else. What do you
think is meant by that?
Even if you are a healthy individual who will not be affected by the virus, vaccinating yourself protects individuals
who are unable to be vaccinated – like those with immunodeficiencies or infants.
8. What other information would you like to know before you deciding whether to vaccinate your children?
Student answers will vary.
Correlation and Causation Analysis
The WHO recommends the first dose of the MMR
vaccination be given when the child is between 9 and 12
months old, with the second dose administered 6
months later when the child is between 15 and 18
months old. Autism symptoms usually begin to present
between 18 and 36 months. Although Autism symptoms
and the MMR vaccine happen to occur at the same time
in a child’s life, does not mean that the two are related.
Correlation does not necessarily equal causation. That is
to say, just because these two things happen to occur at
about the same age, does not necessarily mean there is
a link.
Graph 1 is specifically meant to illustrate the point that
correlation, does not equal causation. There is an
extremely high statistical significance (p<0.0001) between
organic food sales and autism diagnoses. Does
this necessarily mean that organic food causes autism?
Probably not.
Graph 3: Autism and Organic Foods?
Graph 2 shows the likelihood of having autism correlated
with several different factors. For example, it shows that
children who had the MMR vaccine were 0.9x more likely
to have Autism. It also shows children who have a
Cerebellar injury (brain injury) at birth are 36x more likely
to be diagnosed with autism.
Analysis Questions
9. Explain in your own words, what is meant by the phrase
“correlation does not necessarily mean causation.”
Just because these two things happen to occur at
about the same age, does not necessarily mean there
is a link.
Graph 4: Correlations with Autism
10. Based on graph 2, what do you think scientific
research money should be spent on to investigate the
true cause of autism?
I would guess genetic links (based on the twins) and
brain injuries (cerebellar injuries at birth).
11. Figure 3 shows the morbidity from several diseases
before and after vaccines were introduced. What
conclusions can you draw?
Vaccines are effective in providing protection against
many viruses.
Graph 3: Vaccines and Morbidity