How Does the COVID-19 Vaccine Work, and Is It Right for Me?

Jonathan Vellinga, MD

Amazingly, it has only been just over a year since SARS-CoV-2, the coronavirus that causes COVID-19, entered the United States. The nature and severity of the virus prompted a massive race to create a vaccine, and multiple coronavirus vaccines have been created in less than a year. Given that this process generally takes 5-10 years, this is quite a unique moment in history (1)! While some people are marveling at the speed and multi-national collaboration that went into creating these COVID-19 vaccines, others are concerned about how such a reduced study and trial timeline may have affected their safety and efficacy.

How Does the COVID-19 Vaccine Work, and Is It Right for Me?

How are vaccines developed?

The first part of the vaccine-development process involves research, pre-clinical studies, and submission and approval of an application to the FDA (1). After that, scientists begin three phases of clinical studies and trials, testing for safety and efficacy.

Phase 1 trials are short and have a limited number of volunteers. The purpose is to determine that the vaccine meets certain basic safety standards and to identify the most common reactions to the vaccine (1). Phase 2 trials are larger (hundreds of participants), can last years, and help to determine specifics that will make the vaccine as effective as possible, including the exact makeup, number of doses, and more detailed information on safety and reactions (1).

Phase 3 expands even further to evaluate thousands of participants over several years. Once all three phases are complete and a vaccine is determined to meet specific safety and efficacy standards, the developers submit further applications to the FDA to review and confirm that the vaccine is as safe and effective as clinical studies have stated they are (1).

After applications are approved and public distribution begins, the vaccine enters Phase 4. In Phase 4, the vaccine is closely monitored in order to observe safety and effectiveness as more data comes in, and changes may be recommended to healthcare professionals and the public over time based on this data (1).

How do vaccines work?

Vaccines help the body create immunity to a specific disease without the risk of contracting the disease itself. There are a few different types of vaccines, but each leads to a stimulated immune system that produces antibodies, just like it would if you were infected with the disease itself (2). So, when your immune system encounters the virus in the future, your body can react quickly with the antibodies it learned to produce, and effectively mitigate the threat before it can cause you to get sick from it (2, 4).

So, how was it possible that an effective COVID-19 vaccine could be created in under a year? Both unfortunately and fortunately, the world has experienced outbreaks of coronaviruses in the past 20 years that gave vaccine researchers and developers a head start: they knew of the “spike protein” (3,5). Certain viruses have a specific spike-shaped protein that they use to enter cells, and are easily able to multiply and quickly cause widespread infection (3). Scientists in Oxford, for example, had already developed a vaccine for another coronavirus in 2018 that trained the immune system to target and destroy spike proteins. This means that they had a portion of their initial research for a SARS-CoV-2 coronavirus vaccine completed before the disease that causes coronavirus even existed (3). So, once Oxford scientists gathered enough genetic information about the spike protein of SARS-CoV-2, they were able to modify the existing vaccine to create the Oxford-AstraZeneca COVID-19 vaccine, and achieve efficacy much faster than previously thought possible (3,5).

That is just one type of vaccine - aren’t there multiple? How do they differ?

The Oxford-AstraZeneca COVID-19 vaccine is called a viral vector vaccine (3, 5, 6). It creates the necessary immune response to target the spike proteins by introducing a harmless, non-reproducing virus (in this case, called an adenovirus) into the body that contains DNA with the gene for the protein spikes (7). Once this virus enters a cell, the gene is copied, and the cell actually produces the spikes itself. The immune system activates at this point, alerted by both the adenovirus and the spiked cell, and responds by attacking the spike proteins and creating antibodies (5, 7). Another part of the immune system, called helper T cells, detect spikes when the infected cell dies and can help the body build an even stronger immune response to any future spiked viruses that the body encounters (5).