The SARS-CoV-2, or Coronavirus 2019, pandemic has brought the concepts of vaccinations and immunity to the forefront of popular media. It is hard to go a day without hearing about vaccinations on the news as an important milestone in our fight against the virus. Why are vaccines so important in humanity’s fight against disease? How did scientists discover vaccines in the first place? 

Every time you get an infectious disease like the cold or the flu, your body activates an immune response against the specific pathogen, which is a disease causing agent like a virus or bacteria, based on proteins found on that pathogen called antigens. After your body is exposed to a specific pathogen for the first time, it will remember the antigen and be able to combat the pathogen more efficiently for future infections by having immune cells and antibodies ready to fight the pathogen again. 

Vaccines contain the specific antigen proteins for the disease it is preventing, but without a functioning form of the pathogen that causes it. This introduces the antigen to your immune system without making you feel sick! Vaccines are important because they introduce immunity while avoiding sickness, improving health and safety for many.

The concept of vaccinations has been around for centuries. In ancient China, there was evidence that children were exposed to smallpox by having bits of smallpox scabbing from sick people put inside their nose. Techniques like this were also found in Africa, India, and the Middle East. However, it wasn't until a few hundred years ago that organized vaccinations became widespread. 

Throughout the 1500s, smallpox, whooping cough, and measles were very common around the world and spread easily in cities due to the high density of people and poor sanitation conditions. When Christopher Columbus came to America, he and his crew carried these pathogens to the Native American population, who had never been exposed to these pathogens before and had no immune response ready to fight them. Over 80% of the Native American population died of infectious disease, illustrating how important having immunity can be for the safety of populations. In the 1700s, however, Europeans began to realize that people who had been sick with smallpox did not usually get infected again. One man in particular, Edward Jenner, made the observation that milkmaids who worked with cows would never even get smallpox in the first place! Cows were known to carry a disease called cowpox, which is related to smallpox but relatively harmless in humans. Jenner hypothesized that the fact the milkmaids had been exposed to cowpox gave them protection against smallpox, and so he began to test this theory. He took fluids from a milkmaid who had been exposed to cowpox and put them in a cut on the arm of a young boy who never had smallpox. The boy was later introduced to smallpox. He never got sick. After that point, Jenner started the practice of exposing people to cowpox so they would not become sick from smallpox. He called this process “vaccination,” from the latin word for cow, “vacca.”

While this was a groundbreaking discovery at the time, it did not fully solidify the practice of vaccinations. Jenner had no idea what actually caused the diseases, as microorganisms like bacteria were not discovered yet, so vaccines did not become common for other diseases for many years. In the 1800s, another scientist named Louis Pasteur discovered that bacteria were the cause of many diseases. Once it was known what caused disease, scientists had a better understanding of how to use Jenner’s principles to protect people from getting sick. The first widely available lab-made vaccinations were made in the mid 1900’s for diseases like yellow fever and smallpox. By the end of the 1900s, some diseases, such as smallpox and measles, were virtually gone from the planet. Now, it is estimated that vaccines save thousands of lives every year in the United States alone. 

Scientific knowledge on disease and immunity means scientists are able to quickly identify antigens and formulate vaccines for modern diseases such as COVID-19. However, it is also important that scientists ensure the vaccines are safe, effective, and have no severe negative side effects. That is why we have clinical trials. Clinical trials test the effectiveness of vaccines, but they can take many months or years to complete in order to ensure the safety of everyone involved. This is why you hear that a vaccine for COVID-19 may take 12-18 months to develop. This time is important to ensure that scientists can create an effective vaccine capable of halting the spread of COVID-19. In the meantime, you can help keep the population safe by staying at home as much as possible, wearing masks, and observing social distancing.