Vaccines 101: Everything You Need To Know About Our Greatest Medical Marvel

Part 1 of our "World Immunization Week" series

April 24-30 is World Immunization Week, and we at A Plus are proud to present a five-part series that celebrates the incredible impact vaccines have had on global health.

Vaccines are one of the most important tools of modern medicine because they prevent infection from devastating diseases. Unfortunately, a lot of misinformation has been circulating on the topic. The science behind vaccines has been proven again and again, and misunderstandings about them put human lives—particularly those of children—at risk. 

This is only a very brief introduction to immunizations. Those seeking more information are advised to speak to their physician or a friendly local epidemiologist. 


For thousands of years, smallpox was one of the most catastrophic illnesses on the planet. Single outbreaks could kill 1 in 3 of those who were infected. As Europeans began traveling and exploring the globe, the illness decimated populations of indigenous people

A break in the madness came in the 1790s when an English scientist named Edward Jenner noticed that people exposed to cowpox did not contract smallpox. He began deliberately infecting people with cowpox, protecting them from the horrors of smallpox. The technique was refined over the years, creating an effective vaccine.

The World Health Organization (WHO) began a global mission in the mid-1960s to immunize  against smallpox and bring about the end of the disease. That vision was realized in 1980 when the world was declared free of smallpox—the first disease eradication ever.

Today, there are vaccines for a variety of diseases, including polio, chicken pox, measles, tetanus, hepatitis A and B, whooping cough, and many more.

Thanks to decades of dedication from Rotary International and its partners, polio is poised to follow in the footsteps of smallpox as the second disease eradicated through the use of vaccines.

Once polio is gone, other diseases will find themselves in the crosshairs. Additionally, the rates of dozens of other diseases have been reduced significantly thanks to immunization.

How They Work

Michael Schall / A Plus
Michael Schall / A Plus

When the immune system encounters a threat, it must create antibodies in order to destroy it and prevent disease. If a person is exposed to a disease, they develop the antibodies while fighting off infection. If they are exposed to the disease again later on, the body now knows how to fight back. Vaccination creates protection in a way that is similar but much more desirable.

We now know the virus that causes cowpox is very similar to the one that causes smallpox, though different enough to be harmless to humans. However, scientists aren't always lucky enough to find a naturally-occurring microbe that is benign, yet triggers the immune system in the same way as something that causes disease. So, scientists have had to find a way to copy that experience as much as possible.

There are a few main ways of doing this: live attenuated vaccines, inactivated vaccines, and subunit vaccines. 

Attenuated vaccines use a live, yet significantly weakened, form of the microbe (though it works better on viruses). This is one of the easiest ways to create a vaccine and it requires fewer doses to train the immune system to fight the particular illness. While these are generally safe, people who are immunocompromised may not be able to receive them. Additionally, these vaccines also need to be refrigerated, which makes them difficult to transport, particularly in remote areas.

Inactivated vaccines use a dead form of the microbe, making it a lot easier to transport them and immunize people in less developed areas.

Subunit vaccines use only part of the microbe, making it possible to train the immune system to fight off the disease without introducing the part of germ that could cause illness.

When the contents of a vaccine enter the bloodstream, the body's immune system learns to create antibodies capable of destroying the microbe. 

Later on, should an active version of the microbe wind up in the body, the immune system has had enough practice already that it is ready to take it out. The immune system gains the wisdom of dealing with the germ without the person having to go through the trial of getting sick. 

Herd Immunity


Not everybody is capable of getting all of their vaccines for a number of reasons. Some infants aren't old enough to be immunized against certain diseases while others may have allergies to certain ingredients or are immunocompromised in some way that makes it unsafe for them to receive a vaccine. 

If nobody in a group has immunity to a disease, it is easy for the infection to spread. People who are immune act as an insulator, preventing the spread of disease. The more people who are immunized, the better the buffer. Experts believe a 95 percent vaccination rate is required for full-strength "herd immunity."

Some people have a "my child, my choice" attitude toward vaccines, but that mentality fails to view the children as an integral part of creating herd immunity, which is essential to protecting those who cannot be immunized due to age or medical condition. For infants or immunocompromised children, something as simple as a trip to the park can turn deadly if unvaccinated children are harboring and spreading infectious disease.

Fast Facts

Much of the pushback against vaccines is rooted in misinformation, so talking about the actual facts is of paramount importance.

Fact: Vaccines do not cause autism. 

The myth of a link between vaccines and autism began in the 1990s after a study led by Andrew Wakefield came to that conclusion. It was later determined that Wakefield falsified data in the study to benefit his own financial interest (which he failed to disclose). Because of this blatant fraud, the paper was retracted by the journal and Wakefield lost his medical license.

Even when anti-vaccination groups paid for the research, there has never been a shred of evidence to indicate a link between vaccines and autism. 

Fact: The ingredients in vaccines are safe.

Vaccines do contain ingredients that can sound scary if someone has not had the benefit of biology or chemistry classes. 

Formaldehyde is typically associated with the embalming process, so many are concerned that it is used in vaccines to deactivate viruses. However, formaldehyde is naturally produced in the body, where it helps form DNA and amino acids, so the body is more than capable of dealing with it safely. Formaldehyde also exists in the foods we eat, and a child may well get over 100 times more formaldehyde from eating a pear than getting a vaccine.

Other vaccine ingredients, including thimerosal and aluminum salts, also sound far scarier than they actually are.

Fact: It is safer to be immunized than to risk exposure to the disease.

There is an incredibly rare possibility of severe side effects after immunization (on the order of less than 1 in a million for many vaccines), but the possibility of severe complications from actually contracting the disease is closer to 1 in 1000. 

Sure, nobody likes getting a shot from a doctor, but getting a vaccination provides lifelong immunity with only a fleeting moment of discomfort while contracting something such as measles can last days or weeks with a far greater chance of severe side effects including brain damage, loss of hearing, and serious respiratory infections.

Fact: Vaccines are incredibly safe and serious side effects are very rare

In virtually all cases, the worst reaction someone will experience after receiving a vaccination is a low-grade fever and temporary tenderness at the injection site.

Some anti-vaccination advocates cite deaths listed on the Vaccine Adverse Event Reporting System (VAERS) funded by the CDC and FDA as "proof" that vaccines are dangerous. The detail that is most often left out is that VAERS does not indicate any form of cause and effect; just that something happened after getting a vaccine. On the site itself, VAERS advises people to "report adverse events even if you are unsure whether a vaccine caused the event."

Final Word

Vaccines have had an incredible impact on global health, saving millions of lives each year and improving the quality of countless others by preventing harmful diseases. 

Nothing is ever going to be 100 percent safe and vaccines are no exception. There will always be a minute risk of serious side effects, but they are incredibly rare. The diseases themselves are far more dangerous. 

People who cannot receive vaccines due to allergies or severe medical conditions depend on herd immunity, which means that opting out of vaccines without a medical necessity is not just an issue that affects one person: it can have large consequences for the community as a whole. 

As long as there are infectious diseases threatening global health, there will be scientists, doctors, and volunteers working tirelessly to stamp them out through preventative vaccines. 

Help the effort to eradicate polio by donating to Rotary International here. For every dollar that comes in, the Bill & Melinda Gates Foundation will donate $2, which triples the power of the contribution. 

Cover image: Shutterstock