Vaccines: The Truth

By  Melissa Martinez
Intern, Center for Health and Biosciences

Mohini Bindal
Research Assistant, Center for Health and Biosciences

Jonathan LeBeau
Intern, Center for Health and Biosciences


As a parent, it goes without saying that you want the best for your child. When it comes to health-related issues, such as vaccines, it is exceedingly difficult to read through years of research articles in order to make an informed decision. Below is a short summary of what vaccines are and how they work, drawn from evidence-based medical research articles.

So what are vaccines?

Vaccines are a cocktail of ingredients that primarily contain the disease causing agent, the pathogen of interest. These pathogens are inactivated or contain only a fragment of the microorganism such that they cannot cause disease. This allows the body to form antibodies, protein molecules that recognize and fight these pathogens. In future instances of exposure, the body is equipped with the necessary resources and “knowledge” to fight them off and stay healthy. Vaccines give your body the upper hand when it comes to protecting your body against foreign invaders.

Why can’t my body just fight pathogens off naturally? 

As amazing as our bodies are, they are not always strong enough or cannot respond quickly enough to thoroughly protect against the damage these invaders can cause. You can think of a vaccine as giving your body the inside scoop about the particular invader that said vaccine is made to protect against. They provide your body with a short training session against a weakened version of the invader. In this way, your body develops a plan of action to overcome these invaders to be used when needed. Conversely, without the vaccine, your immune system has to respond to a pathogen without any prior experience, and it can take as long as a week before your body conjures up the necessary antibodies to fight back. This means the pathogen has time to wreak havoc on your body in a situation where minutes can mean the difference between life and death.

What about herd immunity?

Herd immunity is a phenomenon in which a group of vaccinated people reduce the likelihood of unvaccinated individuals becoming infected by a pathogen by creating a virus-free environment, one in which disease cannot spread. To follow along the previous analogy, it is akin to the bodies of vaccinated people having manuals for emergency situations. Thereby, when this vaccinated individual encounters a pathogen, the “manual” allows the individual to take care of the potentially disastrous situation so the pathogen isn’t brought back to individuals that have no manual. In sum, the more vaccinated individuals, the safer the environment, protecting at-risk groups that cannot be vaccinated, such as those too young to receive vaccines or people with compromised immune systems.

If everyone in the community is vaccinated, why do I need to get a vaccination?

The answer lies in travelers. If an unvaccinated person is exposed to a pathogen in another country, they are capable of carrying that disease back when they return and infecting others. For example, in one instance described in Nature Medicine, an unvaccinated 7 year-old boy returned home to San Diego after a trip to Switzerland. After falling sick a week later, he was diagnosed with measles. It was later determined by public health officials that he had exposed as many as 893 people to the disease, 11 of which also developed the disease. In particular, one was an infant who had yet to reach the appropriate age for vaccination against this disease and had to be hospitalized.

If the boy was vaccinated, he would not have caught the virus and spread it to others. There are several other cases like this one, in which perfectly healthy individuals choose not to be vaccinated, endangering those around them. Instances like these severely compromise the health of entire populations and are highly preventable when you vaccinate yourself and your children.

How do vaccines decrease transmission of diseases?

When vaccinated for a disease, that pathogen is unable to thrive in the host’s body as it would in an unvaccinated individual. The antibodies in the host body immediately attack the pathogen and eliminate it, curtailing propagation or dissemination of toxins. As a result, the pathogen does not spread as easily from person to person. However, in an unvaccinated individual, the pathogen has time to divide and strengthen as the host body struggles to fight back. In this time, the pathogen spreads easily from person to person, and in the process, may even evolve into a more deadly form. This creates a dangerous situation for people in the community with compromised immune systems.

Which vaccines are required?

The Centers for Disease Control and Prevention has published a list of recommended vaccines needed, by age, that can be found here. Additionally, your primary health care provider can help answer any questions you might have about vaccines.


This is the first of three blog postings on vaccines, written by interns and researchers in the Center for Health and Biosciences at the Baker Institute.

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