Our worst COVID-19 fears have been realized. We’re currently seeing well over 200,000 cases diagnosed per day in the U.S., with out-of-control spread in almost every state. Hospitals and ICUs in particular are overwhelmed, as we warned was possible in the spring. Deaths have topped 3,000 per day. And with Christmas around the corner, cases aren’t likely to recede any time soon.
But finally, there is hope on the horizon. Following a massive effort, two vaccine companies have submitted applications with the Food and Drug Administration (FDA) to receive an Emergency Use Authorization (EUA), which would allow people to start getting these vaccines outside of clinical trials. Pfizer’s EUA application was approved on December 11, and Moderna’s was approved on December 18. Pfizer began shipping their vaccine out, with the first inoculations scheduled on December 14. Moderna will reportedly begin administering its vaccine as quickly as possible now that it’s been authorized. Health care workers and individuals in long-term care facilities are the top priorities for early vaccination. Both vaccines were at least 94% to 95% effective at preventing symptomatic coronavirus infections in Phase III trials, with side effects generally including symptoms such as sore arms and fatigue, along with fever, body aches, and other classic signs of the intended protective immune response.
Not surprisingly, with two vaccines being rolled out by the end of 2020, some questions remain about the science of the vaccines and the logistics of their authorization, approval, and distribution. I spoke with four experts to find out their thoughts on the vaccine itself, the logistics of approval, and what it will mean for all of us in the coming months. Kevin Ault, M.D., FACOG, is a physician and scientist at the University of Kansas Medical Center in Kansas City; Heather Lander, Ph.D., is a virologist currently serving as a senior research development specialist at the University of Texas Medical Branch; Rebecca Dutch, Ph.D., is a virologist at the University of Kentucky, and Dorit Reiss, Ph.D., is a legal scholar with expertise in vaccination at the University of California Hastings College of the Law.
Crucially, both the Pfizer and Moderna vaccines are mRNA vaccines—a type that has not previously gained approval for use in humans. Most of the vaccines we currently use either contain live viruses that have been weakened (such as measles and mumps), organisms that have been killed (like the influenza vaccine), or pieces and parts of a pathogen (such as the vaccines for Streptococcus pneumoniae, hepatitis B, and many others). So, how do these mRNA vaccines work, and why have they been a leading candidate during the pandemic? Keep reading to learn those answers and more.
1. What is an mRNA vaccine, and why are the first U.S. vaccines both this type specifically?
To begin, let’s be clear about the core purpose behind these vaccines, says Lander: “As with all vaccines, those vaccinated with an mRNA vaccine are protected from developing COVID-19 without risking the very real consequences of natural SARS-CoV-2 infection.” For now, as I mentioned above, these two mRNA vaccines seem to be quite effective at preventing symptomatic coronavirus infections. We don’t yet know about the other protections these viruses may confer—I’ll delve into that more in a bit.
Here’s how these vaccines work: mRNA carries the information for how to make a protein, Dutch explains. Specifically, the mRNA in these vaccines carries the instructions for how to make the SARS-CoV-2 spike protein, or a portion of it, depending on the vaccine.?With the actual virus, this spike protein is what enables SARS-CoV-2 to enter a person’s cells and replicate, causing infection. But when our own cells already have the information about how to make this protein, they can generate an immune response to it so they know how to protect us from the virus if we actually encounter SARS-CoV-2 naturally at some point. In order for this protection to happen, though, the vaccine needs to get into our cells in the first place. To make this possible, manufacturers “place the mRNA inside a small particle, termed a nanoparticle, that is made up of [components such as lipid, or fats], and these help ferry the mRNA into cells,” says Dutch. Once inside the cells, the cells make the spike protein, which elicits an immune response.