🦠 A COVID-19 Vaccine Introduction

A vaccine trains your immune system to fight a specific infection. Vaccines have been in use since the 1700s in Europe, possibly much earlier in Turkey, China and India (source).

Vaccines represent one of the most impactful inventions in human history. Many diseases that once ravaged communities have been completely eradicated by vaccines. Between 1924 and 2010 in the United States alone, vaccines prevented an estimated 103.1 million cases of childhood disease (source). In the 1800s, smallpox was responsible for an estimated 300 million deaths. Because of vaccine technology, smallpox was officially declared eradicated in 1980 (source).

Polio is another striking example of the success of vaccines in preventing illness. For over 40 years, Americans feared catching the disease, and public places closed for periods of time to limit the spread. When Jonas Salk developed the vaccine, a collective sigh of relief was breathed by the population. Though polio has not been completely eradicated, there were only 94 cases globally in 2019 and it is no longer the feared epidemic it once was (source).

Vaccines have been able to achieve such amazing success because they cleverly use our own immune system’s natural defense against infection. Like a boxer training with a sparring partner before the actual fight, the vaccine is a safe, controlled practice round for our immune system. If we do come into contact with the disease the vaccine was designed to counteract, our immune system will already know how to fight it because it’s already “sparred” with the disease thanks to the vaccine.

To understand how our immune system fights the virus that causes COVID-19, and how the vaccines help with this fight, we must first understand a little about the virus itself. Severe Acute Respiratory Syndrome Coronavirus 2, commonly abbreviated as SARS-CoV-2, is the technical name for the virus that causes Coronavirus Disease 2019 (abbreviated as COVID-19). As the name suggests, it is a “coronavirus,” a type of virus defined by its spike-covered outer-envelope, which resembles a solar corona when viewed with a special type of microscope. There are many “coronaviruses,” which has led to some confusion. “Corona” is an umbrella term for many viruses, including viruses in animals. Some of these coronaviruses are already vaccinated against in animals. This is why you may see references to “coronavirus” prior to the emergence of COVID-19. It is also one of the reasons the COVID-19 vaccine was able to be developed so quickly (source).

Adapted from an image by Desiree Ho for the Innovative Genomics Institute.

The spikes that protrude from the body of the virus insert into receptors on the surface of our cells, triggering a process by which the virus’s genetic material (RNA) is absorbed into the interior of the cell. This spike and receptor relationship is very similar to how a lock and key work. With its genetic material now inside, the virus hijacks our cell, using it to produce more copies of itself. While not known with certainty yet, each infected cell may produce 600 to 700 new copies of SARS-CoV-2 (source).

Adapted from an image by Desiree Ho for the Innovative Genomics Institute.

Pfizer and Moderna’s vaccines both aim to disrupt this lock and key process using messenger RNA (mRNA). mRNA is a molecular strand of genetic material that holds instructions for building proteins. The Pfizer and Moderna vaccines both deliver mRNA into our cells that instructs the cell to build the SARS-CoV-2 spike protein. The spike protein on its own is harmless, but will prompt the immune system to begin developing a defense against it.

This defense comes in the form of antibodies, special y-shaped proteins built to bind to an antigen. Antigens are anything our immune system recognizes as being foreign. The antigen in this case is the spike protein the mRNA vaccines teaches our cells to build. Recall the lock and key analogy. With an antibody bound to a spike protein, the spike is no longer able to insert itself into our cell’s receptors. A vaccinated individual’s immune system will already know how to fight SARS-CoV-2 if it enters the body in the future by deploying these antibodies.

Adapted from an image by Desiree Ho for the Innovative Genomics Institute.

It's important to note that our current understanding is that the Pfizer and Moderna vaccines do not protect you from becoming infected. Instead, they give your immune system a head start on the virus, resulting in a much milder case of COVID-19. Ten cases of severe COVID-19 were documented among the study participants enrolled in the ongoing Pfizer vaccine trial. Nine of these cases were in the placebo group, leaving only one case in the group that actually received the vaccine (source). It is likely we will hear stories of people getting sick with COVID-19 even after getting vaccinated. It’s important to remember this does not mean the vaccines are ineffective, rather that this person may have suffered a much more severe case of COVID-19 without it.

Concern over any medication is reasonable. Thankfully, at the time of this writing (06-06-2022), we have mountains of data suggesting the vaccines are safe. A recent publication in the New England Journal of Medicine found the Moderna mRNA vaccine to be 94.1% effective at preventing COVID-19 illness, including severe cases. They also found no data to suggest side effects other than temporary local and systemic effects (like rare allergic reactions).

If you have concerns about the vaccines in regards to your personal health history, do not hesitate to speak with your doctor.

The American College of Obstetricians and Gynecologists currently recommends pregnant women and nursing mothers get vaccinated with either Pfizer or Moderna vaccines (source).

No, but this confusion is understandable. The vaccines do use part of the SARS-CoV-2 genetic material, the mRNA mentioned above, but this genetic material never enters into our cell’s nucleus, the location of our genetic material. Even if it did, there is no way this mRNA strand could insert itself into our DNA. RNA is different from DNA structurally and functionally in many important ways (source). The two cannot be interchanged or mixed, just like you cannot swap out sugar for salt in a recipe.