The Immune System

Your immune system is your body’s way of defending itself against foreign bodies. It uses specialized cells called white blood cells (or leukocytes) to attack anything that it doesn’t recognize as “you.” “Being sick” is a battle between you and the foreign bodies. Being able to recognize a foreign body and produce enough antibodies (cellular fighters specific to that particular foreign body) quickly is crucial to this battle.

Vaccines gives your immune system a boost. They act as a training program to prepare your body against the real virus. Vaccines are weakened or dead versions of the real virus, and by introducing your white blood cells to the vaccine, your immune system will create the appropriate antibody and have it stored and ready for when you are exposed to the real virus. Having the antibodies already produced significantly decreases the chances of contracting the disease in the first place, and can help prevent serious illness or death from any infection you may get.

Vaccines are very effective, but they are not perfect. Most people who are vaccinated are fully immune and cannot contract the disease, but a very small portion are only partially immune and may still be susceptible to disease. However, even if the vaccine isn’t entirely effective, it can help prevent serious illness or death for anyone who contracts the virus. This is why it is still important to get a flu vaccine each year, even if the vaccine is “less effective” than they thought it would be. You may receive the vaccine and still contract the flu, but you are less likely to die from it. 

Herd Immunity

Diseases spread through “chains of transmission,” and the chain is dependent upon two things: its infectious rate, and its contagious rate. The infectious rate is the amount of exposure you need to the disease in order to catch it. This can vary from a single virus to several milliliters. A contagious rate is how easy the disease can spread from person to person. For example, some diseases are not contagious but are highly infectious, like malaria: you can’t get it from someone with malaria, but you can get it from a small mosquito bite. 

Infectious and contagious rates are important in calculating how easily a disease spreads, which we express in “reproduction numbers,” called R values. These values tell us how many new cases of the disease can come from each individual case. Low R values mean that it’s very hard to spread whereas high R values mean that it’s very easy to spread.

Photo Credit: Wikipedia: Basic Reproduction Number

Herd immunity occurs when a high enough percentage of the population is immune so as to prevent the transmission of a disease. If someone with the disease is surrounded by people who are immune, then they can’t pass the disease on to someone else. When we talk about herd immunity, we talk about “chains of transmission” – pathways that the disease can take from infected person to susceptible person. The required level of herd immunity needed in order to keep a disease at bay is dependent upon that particular disease and its R value. 

Target vaccination rates are based on these R values. In order to prevent an outbreak, you want to infect no more than one additional person for each case. So for a disease with a low R number, say influenza (R=2), you’re only going to pass it on to two people. If half of the population is immune, only one person will be infected per case, and it won’t cause an outbreak. When the immunity level is high enough, the possible chains of transmission are interrupted, and the disease is contained. This is really important for children who are too young to receive vaccinations, individuals who have compromised immune systems, and those who are too ill to receive vaccines. They rely on broken chains of transmission in order to stay healthy. 

Photo Credit: NAID

Measles has a very high R number, and it’s airborne; as a result, the goal for measles vaccinations is around 90-95% of the population. Taking into consideration the number of individuals who can’t get vaccinated, that leaves very little room for people choosing not to vaccinate. Unfortunately, due to vaccine hysteria, immunization rates have been falling in different areas as some people are choosing to refuse vaccinations, and herd immunity is breaking down, placing individuals who are already highly susceptible to illness in more danger. This is compounded when people who don’t vaccinate tend to cluster into groups, increasing the likelihood that they will pass deadly diseases between them, making it considerably easier for the disease to spread to those who either have incomplete protection through their vaccination or no protection because they can’t be vaccinated. As a result, we’ve had a resurgence of several deadly diseases in recent years which the CDC monitors and tracks. 

In 1988, Andrew Wakefield, a former physician and researcher published a falsified study linking vaccines to autism. After other researchers failed to reproduce his findings, an investigation revealed that Wakefield had falsified his data and had used unethical procedures. He lost his license and has been barred from practicing medicine. 

Despite not a single other study showing any relationship between vaccines and autism and monumental evidence that vaccines are incredibly safe and effective, this single publication launched a anti-vaccination movement. Combined with the opinions of celebrities like Jenny McCarthy and Dr. Bob, it has triggered a disease resurgence in the United States. Parents, fearing over-exaggerated consequences of vaccinations, are instead opting for exposing their children to the actual disease.

As a result, the twenty or so individuals who travel globally and bring measles into the United States each year are now triggering major outbreaks throughout the country. 2014 saw the highest rate of measles in the US since 1994, and these outbreaks are largely occurring in areas where vaccine coverage is significantly below average. Measles can kill 10% of those it infects, and there have been over 6,000 preventable deaths since 2007 when the anti-vaccination movement started to gain momentum. Thankfully, deaths seem to be dropping with increased efforts toward education and stronger vaccine requirements. 

There are many misconceptions about vaccines and diseases. You can find several of them below, along with explanations. For links and more in-depth answers to some of these questions, see the Resources tab. 

Diseases disappeared because of sanitation and other medical care, not vaccines.

While people were more likely to survive diseases because of improved medical care, the contraction of diseases did not begin to slow significantly until the introduction of vaccines. Even today, many vaccine-preventable diseases like the measles or tetanus are deadly and have long-lasting complications.

Improved sanitation did have a small impact on preventing the spread of some diseases, though this depends on how each particular disease spreads. Decreased person-to-person contact (decreased population density), improved waste management, and better food safety techniques can only prevent diseases that are spread through those vectors.

One way we know this for sure is to compare disease rates in countries whose conditions haven’t measurably changed but whose access to vaccines has. For example, the HPV vaccine was introduced in 2006. In countries with high HPV vaccination rates, this has decreased their infection rates by 90%, with no significant change in sanitation. As 1 out of every 100 people who contract HPV will develop cancer because of HPV, and approximately 50% of people contract HPV without the vaccine. While at the same time, the rates of contracting chickenpox, which has no vaccine, has not changed regardless of improved sanitation and medical care.

Diseases began disappearing before vaccines were introduced.

A very popular argument is based on this graph, showing that mortality rates of diseases began dropping long before vaccines were introduced. 

Image result for vaccine deaths graph
As you may have figured out from above, this graph is misleading for one simple reason: it depicts mortality rates, not contraction rates. Vaccines prevent the contraction of a disease. Increased medical care can prevent deaths from these diseases, but if you want to know how effective vaccines are, you need to compare contraction rates. You can see the effects of the measles vaccines on the number of cases per year below. 
Image result for vaccine contraction graph
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Getting combination vaccines is dangerous

Some parents worry about combination vaccines, which are vaccines that are combined into a single shot. They fear that this may be overwhelming to their child’s immune system and contains unnecessary chemicals. 

In reality, a child’s immune system is exposed to millions of germs each day and is capable of responding to many disease threats at once. Vaccines are less challenging than many of the diseases that the immune system must respond to on a regular basis, so having a single shot with several vaccines is no more taxing on an immune system than every day life. The side effects of combination shots have been shown to about the same as single shots of the same vaccine. 

A huge side effect of combination vaccines is that it allows your child to be given protection as early as possible. Spacing out vaccinations leaves your child vulnerable unnecessarily. It also minimizes the number of shots your child receives and the number of office visits you have to make, saving you both time and money while making it easier for your child. 

For more information on combination vaccines, see our resources tab. 

Mercury in vaccines is dangerous

Of the most common concerns centers on the fear that mercury is present in vaccines in the form of Thimerosal. 

Thimerosal is a preservative for multi-dose vials of vaccines that prevents the growth of fungi and bacteria inside these vials. Multi-dose vials is a very cost-effective and efficient means of giving a single vaccine to many people. Without these vials, separate vials would have to be kept for each syringe used. Multi-dose vials are especially important for vaccines in areas without good access to sanitation as, without these vials, people will not be able to receive as many vaccines as they should. 

Many people express concern that Thimerosal contains mercury. While this concern is understandable, it is important to understand that the presence of mercury itself is not an indication that it may be dangerous. Mercury is an element, and like all elements, combine with other elements to produce compounds. The potential danger of a compound is completely unrelated to the elements that combine to form it. For example, both sodium and chloride are elements that, on their own, are very dangerous. Combined, they produce table salt, something completely harmless. So to know whether or not Thimerosal is dangerous, you need to know what happens to it in the body. 

Once Thimerosal is in the body, it breaks down (or metabolizes) into two compounds: Thiosalicylic acid and ethylmercury. Ethylmercury is the compound that contains the mercury atom and is a very stable and common form of mercury. It flushes out of the body very rapidly, and there is no evidence that links it to any harm. 

Many people confuse ethylmercury with methylmercury. Methylmercury is a form of mercury that accumulates in living organisms (called “bioaccumulation”) and is toxic in small amounts.  These two forms are similar because they both contain the mercury atom, but they differ structurally (see below) and functionally. Methylmercury is dangerous, but ethylmercury is not. One cannot become the other, and there is no reason to be concerned about the presence of ethylmercury.  

The first molecule is methylmercury. The second is ethylmercury. Notice the additional “functional group” on the ethylmercury (the carbon and hydrogen group). This changes how this compound reacts and breaks down. Source:

The concerns over mercury in vaccines comes from a misunderstanding of the differences between ethylmercury and methylmercury. The fear of ethylmercury became so great that Thimerosal has been removed from virtually every type of vaccine in 2001. While there is no risk associated with ethylmercury, it was thought best to remove it so that people would be more likely to vaccinate. The fear of the ethylmercury was greater than any real danger it posed, but the fear kept people from getting much-needed vaccines.

Vaccines cause autism

This is where the current vaccine scare started. Andrew Wakefield’s now retracted paper claimed that the MMR vaccine is responsible for the rise of identified cases of autism. While this study was completely fabricated, many still believe vaccines are the cause.

One reason this theory is so popular is because the symptoms of autism often begin appearing around the same time as regular vaccinations. Developmental delays and regressions begin appearing between 1 and 2 years old, and this is also when children begin receiving a lot of their vaccinations. But just because things happen at around the same time does not mean that one causes the other. We call this a correlation/causation fallacy. 

There are several lines of evidence that do not support this claim. For one, there are many documented cases of autism appearing in children who were not vaccinated. If vaccines caused autism, we wouldn’t see this. We’ve also conducted long-term studies tracking the timing of vaccines with autism diagnoses, and there is no evidence they are related.  One very significant study published in 2015 in the Journal of the American Medical Association analyzed 95,727 children, and they found no evidence supporting any link between the MMR vaccine and autism (the study can be found here). To date, there is not a single study that links the rise of autism with vaccines of any kind. The American Academy of Pediatrics, the preeminent national organization for pediatrics, has created a website devoted to collecting and summarizing these studies. You can find that website here

Many scientists are trying to understand the cause of autism, and a great deal of research is being conducted. There are several things that seem to influence autism, including genetic, epigenetic, and environmental factors. There are particular genes that seem to be strongly correlated with the appearance of autism, which explains why it tends to run in families. Environmental factors, such as parental age and birth spacing, also seems to influence it.

Epigenetics, which is an environmentally-influenced effect on how genes are expressed (or read), also seems to play a significant role. Environmental conditions, like diet and exposure to pollution, can change which genes are expressed, essentially turning them on or off. Some of the strongest evidence for the occurrence of autism seems to come from epigenetic effects (like the effect of a maternal grandmother smoking).

More evidence that autism is not caused by vaccines comes from research on characteristics of autism that begin to appear in utero. Autism is significantly correlated with particular facial features that begin to develop prenatally. These features could not be caused by vaccines that they receive later in life.  

Delaying vaccines is safer

Many who are hesitant to vaccinate choose to compromise, preferring a delayed schedule and spacing out the vaccinations. Their main concern is usually compound vaccines, fearing that they would cause an immune system overload.

However, as mentioned above, compound vaccines are no more likely to cause negative side effects than single vaccines, and our immune systems are fully capable of accommodating compound vaccines. Delaying vaccines does not decrease any risk of vaccinating and only increases the risk of exposing a child to dangerous diseases when they are most vulnerable. 

The risk of the vaccine is greater than the risk of the disease

Some people believe that the risk associated with getting a vaccine is greater than the risk of the disease itself. As described above, the actual risk associated with a vaccine is very low.

Many who assert this point to the “inserts” listed with vaccines. These inserts list all of the reported conditions reported during the medical trials of that vaccine. However, the fact that a condition occurred during a trial is not an indication that the vaccine caused that condition. The inserts are required to list all conditions that occurred at the same time – including car accident deaths and sexually transmitted diseases – which are clearly unrelated to the vaccine. The inserts also include language indicating any increased risk of the vaccine for these conditions, and for the vast majority of conditions, they are no more likely to occur with a vaccination than they are with those in the placebo group. 

Only children too young to receive vaccines and those whose immune systems are compromised (from an autoimmune disorder, cancer treatments, or other medically-diagnosed conditions) run any serious risk from a vaccine. These people are unable to receive vaccines as their immune systems are too weak to respond positively to them. They rely on the rest of the population to receive vaccines, keeping their chances of encountering the disease very low. 

The unfortunate reality is that the diseases that vaccines protect against can have serious side effects. Contraction of measles can cause blindness, severe diarrhea (less than 1 in 10), pneumonia (1 in 20, leading cause of death for children who contract the measles), ear infections that can cause permanent hearing loss (1 in 10), encephalitis (1 in 10) and death (1-2 in 1,000). While medical technology has improved our ability to respond to these diseases, deaths still occur, especially in populations without adequate medical care. 

Additionally, the longer a disease exists in a population, the more it can evolve, becoming immune to the drugs that we have used in the past to treat those who fall ill. We use anti-viral medications to treat viral infections, and antibiotics to treat bacterial infections. With both of these, we run the risk of these diseases developing a resistance to the treatments. This happens when we overuse these medications or do not take them as indicated. This is especially true with antibiotics, and many strains of bacteria that cause deadly diseases in humans are evolving antibiotic resistant strains. Each contraction of and treatment for a virus or a bacteria gives is the opportunity to mutate and develop resistant strains. 

For example, pneumonia is a secondary infection that occurs in 5% of those who contract the measles. It is most often caused by a bacteria or a virus. Unfortunately, bacteria-causing pneumonia is becoming resistant to our antibiotics, and some of the newest strains are resistant, deadly, and highly contagious. While those who contract the measles may not die from the measles, they very well may die from the pneumonia they contract because of the measles.  

The Wakefield Scandal
Children’s Hospital of Philadelphia (CHOP): “The Wakefield Studies”
Helio: Uncovering the Truth

Wakefield’s Retracted Paper
Indian Journal of Psychiatry: Peer-Reviewed Summary of the Scandal

Diseases, Vaccines, and Sanitation
WHO: Common Misconceptions
Science-Based Medicine: “Vaccines didn’t save us”
History of Vaccines

Combination Vaccines
CDC: Combination Vaccines
Journal of Global Infectious Disease: Effectiveness of Combination Vaccines in Reducing Disease 

Thermiosal and Mercury
CDC: Thermiosal
CDC: Thermiosal Fact Sheet
WHO: Thermiosal Statement
Journal of Applied Toxicology: Comparison of Ethylmercury to Methylmercury
Neuroscience Fundamentals: Comparison of Ethylmercury to Methylmercury

Vaccines and Autism
The American Academy of Pediatrics: Collection of Evidence
Children’s Hospital of Philadelphia (CHOP): Fact Sheet
History of Vaccines
CDC: “Vaccines Do Not Cause Autism”
Southern Autism Research & Resource Center (SARRC)
Autism Speaks
Science-Based Medicine: “Vaccines & Autism”

Causes of Autism
Autism Speaks: What Causes Autism
American Speech-Language-Hearing Association: Causes of Autism
Autism Speaks: Epigenetics
Frontlines of Neurology: Epigenetics and Autism
International Journal of Environmental Research and Public Health: Epigenetics and Autism
Nature: Epigenetics, Autism and Smoking in the Maternal Grandmother
Molecular Autism: Autism and Facial Features

University of Missouri: Autism and Facial Features

Package Inserts
Harpocrates Speaks

Other FAQs
CDC: Common FAQs
CDC: Parent FAQs
Oxford Vaccine Group