As of last month, both Moderna and Pfizer have successfully cleared clinical trials for their COVID-19 vaccines. The immunizations are now being distributed around the world with a total of 13 million doses administered globally and 4.66 million doses administered in the US. While this number is significantly smaller than the 20 million US doses promised by end-of-year, the fact that these companies have managed to develop and distribute their respective candidates in just about nine months is a feat of its own. Before these vaccines become widely available, we’ll take a science-heavy look into how they work and some of the terminology thrown around when discussing them.
How do they really work?
Coincidentally, the Pfizer vaccine and the Moderna vaccine are incredibly similar in form and function. They are both what are called mRNA vaccines, which work in the following way:
First, the mRNA which codes for a protein on the surface of coronavirus is extracted and placed into a harmless virus that makes up the core of the vaccine. Specifically, both Moderna’s and Pfizer’s vaccines target the characteristic spike proteins, or s-proteins of COVID-19, shown below in red. These proteins play a large part in infection, as they mediate the entry of viral cells into healthy cells.
The harmless viruses, which now display the same spike proteins as COVID-19, are then injected into the patient’s upper arm. There, they are taken up by antigen presenting cells (APCs), which isolate the spike protein and present it to CD4+T cells, or helper T-cells. The helper T-cells then have two separate functions. First, they activate CD8+Y cells, or killer T-cells, and prime them against cells displaying the spike protein. As their name suggests, killer T- cells then seek out these infected cells and induce apoptosis, or cell death, within them.
The second and arguably more important role of helper T cells is the activation of B-cells. Once activated, B-cells turn into plasma cells and produce antibodies which bind to the spike protein, neutralizing the ability of coronavirus cells to infect healthy ones. Additionally, some B-cells remain dormant as memory B-cells, which strengthen your body’s immune response the next time it encounters COVID-19. In conjunction, these factors create a highly effective vaccine.
Efficacy vs. Effectiveness
Another buzz word used when describing these two vaccines is efficacy. You may have heard that in clinical trials, both vaccines have been shown to have about 95% efficacy, meaning that the number of COVID-19 cases in the vaccinated group was 95% lower than that in the placebo, or control, group. However, we must remember that efficacy determined by clinical trials where the patients, their treatment, and their subsequent health are all closely monitored. In essence, vaccine efficacy is how well the vaccine combats infection in perfect or near-perfect conditions. On the other hand, vaccine effectiveness is a measure of how the vaccine performs once released to the greater community. Here, factors like proper storage and correct dosage timing will come into effect. Thankfully, Moderna’s vaccine can be stored at reasonably attainable temperatures, but the Pfizer vaccine raises concerns due to its need for extremely cold temperatures well past the current capabilities of most distribution centers. We have yet to see any statistics regarding the effectiveness of the Pfizer and Moderna vaccines, but we can almost guarantee that these numbers will be lower than 95% and they certainly won’t be 100%. Thus, even once the vaccines have been widely distributed, masks may still be a necessary prevention device.
Side Effects
Finally, we get to the aspect of COVID-19 vaccines that’s making some people a bit hesitant: side effects. The most common side effects of the coronavirus vaccines include fever, chills, and headaches – a relatively small price to pay considering the current situation. In recent news, some patients have seen adverse reactions between the Moderna vaccine and botox fillers, bringing up worries about allergic reactions. Admittedly, evidence has shown that allergic reactions to the current vaccines are much more common than usual but still very low – about 1 in 100,000 for COVID-19 vaccines while the normal rate is about 1 in 1,000,000. In all, with proper preparation on the patient side, both the Moderna and Pfizer vaccines appear to be safe.
Closing Thoughts
Both Moderna and Pfizer produced their COVID-19 vaccines at lightning speeds. This shines a hopeful light on vaccine development as a whole, serving as a testament to what can be achieved through proper funding and resource allocation. Of course, the Coronavirus pandemic isn’t going to disappear overnight, but these vaccines have brought us one step closer to normalcy. It may be a bit longer of a wait until most of us can get immunized, but what’s a few more months?