The History of Vaccines and How They Work

In the current climate of public health discourse, societies worldwide are anxiously waiting for a vaccine that might curtail the rapid spread of a virus that has brought modern life to a crashing halt.

Vaccines have in recent times been a source of great contention between those who support them as compulsory public health tools and those who vehemently believe that they are harmful and should, therefore, be considered elective. The controversy surrounding vaccines can arguably be attributed to fear of the concept of the vaccine itself.

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Many people are afraid that vaccines cause irreversible damage by overloading the immune system with pathogens. Others believe that vaccines are a ploy by big governments. Both of these schools of thought stem from arguably valid mistrust engendered by centuries of unethical behavior in medical experimentation, and a more recent trend of distrust in the pharmaceutical industry. However valid the fears that trigger this debate may be, it is important for people on both sides to understand exactly what a vaccine is and how it works. Political opinions and collective memory aside, the science behind a centuries-old practice that has saved millions of lives is worth exploring. 

How Do Vaccines Work

Vaccines work to prevent disease by helping the body develop natural immunity to certain diseases. They can be administered orally or through injections. Put very simply, vaccines allow your body to respond to a disease by essentially allowing it to “practice” an immune response against a dead or weakened form of the disease.

Being exposed to the altered form of a pathogen through a vaccine allows your body to produce an immune response that will be triggered upon exposure to the actual pathogen. The immune system essentially “remembers” how to respond and quickly produces antibodies for that pathogen before it has the chance to make you very ill. 

There are several different types of vaccines. Live-attenuated vaccines contain weakened forms of pathogens. These produce a very strong immune response and thus are extremely effective in preventing diseases. The drawbacks to live-attenuated vaccines are that they may be unsafe for people with weakened immune systems and that they often require refrigeration, making it difficult to transport them or keep them alive in hot conditions. Live vaccines prevent illnesses such as measles, mumps, rubella, chickenpox, yellow fever, and smallpox.

Another type of vaccine is the inactivated vaccine, which uses a dead form of the pathogen. These vaccines are not as potent as live vaccines, meaning that they often require several doses over time. Inactives vaccines are used for protection against the flu, polio, hepatitis A, and rabies. Subunit and conjugate vaccines use segments of a pathogen that will trigger an immune response that will attack key components of a disease-causing pathogen. These also may require several injections. Subunit and conjugate vaccines are used to prevent diseases such as pneumonia, hepatitis B, meningitis, shingles, and whooping cough.

Toxoid vaccines utilize a toxin produced by the pathogen instead of the pathogen itself. Toxoid vaccines may also require several injections over time to continue protection against the bacteria. These vaccines are used to protect us from tetanus and diphtheria. In addition to the aforementioned vaccine types, scientists are also working on DNA vaccines which may prove to be less expensive and more effective than previous versions of vaccines. 

What Are Vaccines Made Of

Vaccines vary in their ingredients but may be made of the following materials in different combinations. Antigens are small parts of pathogens that alert the body to an infection. Adjuvants (such as aluminum) help the body produce a stronger immune reaction, and can thus lower the number of doses necessary for immunity. Vaccines also usually have antibiotics to prevent the growth of unwanted bacteria in the vaccine. Preservatives and stabilizers are also necessary for vaccines. Gelatin, egg protein, and MSG are common ingredients. Some vaccines also contain formaldehyde to prevent bacterial growth or to inactivate viruses. This formaldehyde is usually present in very small doses. Ethylmercury is present in the influenza vaccine, which also has a mercury-free version. While some of these ingredients may be surprising, scientists work diligently to design vaccines that have very low risks of causing harmful reactions due to their ingredients. 

When Were Vaccines Invented

Vaccines may date back to the year 1000 CE, where evidence has been found of a Chinese inoculation against smallpox. This practice also took place in Turkey and Ethiopia and eventually would become global. Inoculation for smallpox in those times and places involved variations of cutting a patient and placing a smallpox pustule inside the wound.

The modern concept of vaccination was furthered by scientists Edward Jenner and Louis Pasteur. Edward Jenner was an English doctor who discovered a way to protect against smallpox in the 1790s by using the pus of the less dangerous cowpox disease to inoculate a small boy.  After this first use of a rudimentary vaccine, Jenner continued the development of methods and focused on safety lead to the widespread use of vaccines. Louis Pasteur, another pioneer in the field of vaccines, made the first vaccine. He used a weakened form of the bacteria that caused chicken cholera and was able to give chickens immunity to the disease. He would go on to discover the vaccine for anthrax in cows, and eventually the vaccine for rabies in the 1880s. 

Despite the amount of time that people have been working to develop vaccines, they are still being developed as illnesses develop and especially in the cases of epidemics. When people are vaccinated at large percentages, they protect the most vulnerable in their society, by being less likely to contract and therefore pass an illness around. This concept is known as herd immunity.

Today, most children follow an immunization schedule, getting vaccinations against specific illnesses at certain ages, as mandated by their governments. This practice has eliminated the spread of and fatalities from preventable diseases worldwide. As societies began to flourish without the fear of diseases such as measles, smallpox, and polio, some people began to resist the idea of immunization, citing numerous reasons against their efficacy. As the political debate continues, it is important to remember that regardless of opinion, the history and science of vaccines is knowledge that should be available to everyone. The World Health Organization supports a website called the History of Vaccines that provides additional information on this much-discussed topic.