The vaccine trial results from Pfizer and Moderna have given the world much-needed hope that we may soon have the weapons required to end the COVID-19 pandemic once and for all. But it’s important to understand that both vaccines are based on the latest scientific advances. If this pandemic had broken out even five years ago, such vaccines would probably not have been possible. Here, Techonomy offers a brief explainer to help understand why these vaccines are so promising — and so different from their predecessors.

Are these like regular vaccines?

Most vaccines work by introducing your immune system to a weakened or inactive virus. Your body mounts a half-hearted immune response that’s just enough to trigger long-term protection, but not enough to really go haywire. This is the basis for most vaccines we have, from measles to chicken pox to polio. Even your annual flu shot is based on this technique.


Pfizer and Moderna, separately, each used an entirely new approach to creating a vaccine, using a genetic tool called mRNA (short for messenger RNA). Scientists have theorized that teaching the body to spot just a small piece of a virus could be enough to build up immunity. Instead of exposing someone to the entire SARS-CoV-2 virus, researchers this time are utilizing the genetic code of one characteristic piece of the virus — the spike protein. That protein on its own isn’t dangerous or contagious, but it is a key part of the virus that the immune system can learn to recognize and attack, just as it does during a real SARS-CoV-2 infection. Like traditional vaccines, the immune response elicited can give recipients symptoms such as muscle aches and a low-grade fever. The recently-announced trial results, showing effectiveness of about 95% for both vaccines, offer strong evidence that this concept works.

Why did we need a new type of vaccine?

Traditional vaccines take a long time to design, test, and manufacture — 10 years is about average. Even when the vaccine design process is much faster, such as for the annual flu shot, it can still take a long time to produce enough virus content to make each dose. Flu vaccines, for example, are often tested and manufactured by injecting the flu virus into chicken eggs, waiting until the virus has had enough time to replicate, and then retrieving those virus particles to create vaccine doses.

In addition to taking too long to combat the pandemic, the traditional vaccine approach is not safe for everyone. While healthy people can easily withstand exposure to a weakened virus, people with compromised immune systems sometimes cannot. That’s a big swath of the population, including transplant patients, cancer patients, and many elderly people. But because mRNA vaccines are not introducing even a weakened form of the disease into the body, there’s no risk anyone will contract COVID-19 from them.


What does it mean to have an mRNA vaccine?

mRNA is a genetic code that tells your body to build a certain kind of protein. Because the Pfizer and Moderna vaccines don’t depend on injecting people with an entire virus, the tiny piece they need doesn’t have to come from the actual SARS-CoV-2 virus. Once scientists identified the piece of the virus genome that contains the blueprint for the spike protein, they could isolate it and build those same mRNA instructions with the latest synthetic biology tools. That’s why this vaccine can be produced and manufactured at speeds never before imaginable in vaccine development. All the pharmaceutical companies are doing is creating strands of genetic material that tell how to create the spike protein. Once the vaccine is delivered, each person’s body actually builds it using their own genetic machinery, and that protein is enough to teach the immune system how to respond if it ever again sees that same spike protein — which it would if it were exposed to the SARS-CoV-2 virus.

While there are some other mRNA-based vaccines in human trials, this concept is so new that there are currently no approved mRNA vaccines on the market. This kind of technique “may actually revolutionize the field of vaccinology,” said Carlos del Rio, a scientist at Emory University who has been part of some of these vaccine trial studies, in a presentation at the recent annual meeting of the Association for Molecular Pathology. Results indicate that the mRNA vaccines for COVID-19 stimulate both B cells and T cells, two key elements of long-term immune protection.

How long will it take to vaccinate everyone?

Del Rio predicted in his talk that it will take until September or October of next year to vaccinate everyone in the U.S., but added that “vaccinating the world is going to be a big challenge.” He believes we will need many more vaccines to reach all people. The intense cold (-70 degrees Celsius) needed to store the Pfizer vaccine, for example, is likely a deal-breaker for places where fast shipping and reliable electricity are not common. (The Moderna vaccine also must be stored at freezing temperatures, but at -20 Celsius, just slightly colder than a normal kitchen freezer.)

What don’t we know yet?

With two new vaccines for a recently-emerged pathogen that are created based on novel scientific techniques and tested in abbreviated trials, it’s no surprise that there would still be questions to answer. Vaccine trials so far have not included children younger than 12 or pregnant women, for example, so those two key demographics will require further study to determine if the vaccine is safe for them. Scientists also don’t know yet whether people will need the vaccine once (in one or two doses, depending on the type — both new mRNA vaccines are expected to require two doses) or if it will need to be administered again and again over time, like the flu shot. Finally, the accelerated vaccine trials used for the pandemic could not provide the usual long-term view of vaccine recipients. Without a two-year follow-up, it remains unclear what the long-term effects of these vaccines may be.

If you’re such a fan, are you going to get the vaccine?

I am eagerly awaiting my chance to get one of these vaccines. Since I’m not among the groups first eligible for treatment, I’ll have to wait several months for my turn. During that time I will be keeping a close eye on data about safety and side effects, but assuming these vaccines continue to work as well as they have in their trials, you can count me in. For what it’s worth, here’s my rule of thumb: if respected scientific experts like Anthony Fauci are willing to take the vaccine, it should be safe for the rest of us.