What’s in The Vax? Differences Between mRNA and Adenovirus Vaccines

As vaccinations for COVID-19 become commonplace over the following months and potentially years, some new terms and technologies will be thrown out in the public eye that many aren’t familiar with – specifically, the types of vaccines being offered and what the differences are between them. And, while not all vaccines are created the same, they have all proven to be incredibly effective at combating this pandemic and getting our world one step closer to the normal we all enjoyed in 2019 – so, we will always recommend you get vaccinated not based on which of these vaccines you can receive, but on getting vaccinated and protecting yourself as soon as possible.

mRNA Vaccines

Currently Available Types: Pfizer, Moderna

Pros: High Efficacy, No Preservatives, Non-Infectious

Cons: Requires Two Doses, Not Previously Utilized for Public Use

Common Misconception(s): No, they cannot alter your DNA in any way, shape or form

mRNA vaccines are a new type of vaccine to protect against infectious diseases. To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies. Not mRNA vaccines. Instead, they teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. That immune response, which produces antibodies, is what protects us from getting infected if the real virus enters our bodies.

COVID-19 mRNA vaccines give instructions for our cells to make a harmless piece of what is called the “spike protein.” The spike protein is found on the surface of the virus that causes COVID-19. Think of it like a LEGO kit for your body. The vaccine gives your immune system the instructions it needs to build a suitable defense against future infection. It’s what naturally occurs when you get sick; your body begins building an immune response and making antibodies that prevent (or lessen) your chances of getting sick again in the future.

Beyond requiring two doses for maximum effectiveness unlike traditional vaccines, the only real drawback to mRNA vaccines is that they have not been utilized for public use before COVID-19. But researchers have been studying and working with mRNA vaccines for decades. Interest has grown in these vaccines because they can be developed in a laboratory using readily available materials. This means the process can be standardized and scaled up, making vaccine development faster than traditional methods of making vaccines. That quickness is why they were so fast to receive approval; not because they weren’t thoroughly tested, but because they work differently and can be developed faster than any other vaccine we’ve used before.

In lab settings and research, mRNA vaccines have been studied before for flu, Zika, rabies and cytomegalovirus (CMV). As soon as the necessary information about the virus that causes COVID-19 was available, scientists began designing the mRNA instructions for cells to build the unique spike protein into an mRNA vaccine. Beyond vaccines, cancer research has used mRNA to trigger the immune system to target specific cancer cells.

One of the more incredible ideas about future mRNA vaccine technology is that it may allow for one vaccine to provide protection for multiple diseases, thus decreasing the number of shots needed for protection against common vaccine-preventable diseases.

​Adenovirus-Vector Vaccines

Currently Available Types: Jannsen (Johnson & Johnson)

Pros: No Preservatives, Single Dose, Extremely Stable, Older Technology

Cons: Slightly Lower Efficacy, Possibility of Pre-existing Immunity

Common Misconception(s): No, pregnant women do not experience different side effects

Of the six vaccines backed by Operation Warp Speed, the adenovirus vectored vaccines are the only other vaccines, besides mRNA vaccines, to make it to Phase III testing.

Like mRNA vaccines, the main idea behind this type of vaccine is to get genetic material that encodes COVID-19 genes into your cells and can get them to make the virus proteins. The main difference is in how they do this: Where the mRNA vaccine is just the mRNA protected by a chemical shell, adenovirus-vectored vaccines use a virus we know is harmless to act as a Trojan horse. But instead of hiding Greek soldiers, or anything dangerous, the adenovirus releases genes that encode the spike protein.

Adenoviruses are a family of viruses that have hundreds of members, and most don’t cause any known disease or only cause mild “common cold”-like symptoms. Scientists developed a way to use strains of adenoviruses that don’t cause disease as a delivery system for vaccines. So we’re using one virus to deliver the vaccine against another. Where that can, in some rare circumstances cause an issue is that, if you have immunity to the adenovirus from previous, natural exposure, it could reduce the vaccine’s ability to deliver the vaccine because your body will reject the delivery system. It’s very rare, but still a possibility.

The major benefit to this style of vaccine, beyond only being one dose instead of two, is that adenoviruses are incredibly stable. They can be kept for months in refrigerators with no known adverse effects, making them perfect for mass usage outside of a clinical setting. The downside to that single dose is the efficacy, which drops from the high 90s to the mid 70s. But you also get that protection faster because you’re not waiting for your second dose appointment and for that second shot to take full effect. It’s definitely a give-and-take situation, but one that still provides an incredible amount of protection from COVID-19.

No matter which vaccine you choose, you’ll be receiving an important step in fighting COVID-19 not only for you, but for everyone around you. If you think of getting sick from disease and letting your immune system fight it off as “on-the- job training,” then vaccines are the equivalent of college for your immune system. Vaccines teach the immune system how to recognize diseases, so that when you are exposed to the real disease, your immune system can respond immediately. Ideally, you’ll never even know you were infected. This allows your immune system to develop the cells and proteins it needs to fight off the pathogen when they come across the real disease. For you personally, it means fewer sick days and less chance of serious illness and/or long-term effects. For the public, it means less strain on hospital staff, less risk to essential workers and, one day, all of us hopefully being able to take our masks off, hug our grandparents and enjoy life with a little less caution.  

While we will not likely eliminate the SARS CoV-2 virus completely from the population with any vaccine, it is important to try to eliminate as much severe disease and death from this virus. All three of the vaccines that have been authorized by the FDA have shown to be 100% effective against preventing hospitalization and death due to COVID-19 disease.