Trevor James
There are two types of vaccines currently available for COVID-19 in the United States: mRNA and non-mRNA (protein subunit) vaccines. mRNA vaccines are a relatively new type of vaccine that contains genetic material that teaches the body to make a protein that triggers an immune response. This is done by giving cells the instructions to make the spike protein, which is unique to SARS-CoV-2, the virus that causes COVID-19. On the other hand, non-mRNA vaccines like Novavax's protein subunit vaccine contain pieces of the virus, including the spike protein, to trigger an immune response.
| Characteristics | Values |
|---|---|
| Safety | mRNA vaccines are non-infectious and do not interfere with DNA. |
| Efficacy | mRNA vaccines are rapidly degraded in the body and do not easily enter cells. However, recent technology has increased the stability of mRNA molecules, improving cell delivery efficiency and stimulating a more robust immune response. |
| Production | mRNA vaccines can be quickly designed and scaled up. |
| Working | mRNA vaccines train the body to recognize and fight harmful substances like viruses. They do this by providing cells with mRNA instructions to create unique proteins that trigger an immune response. |
| Examples | COVID-19 vaccines are currently the only available mRNA vaccines. |
| Side Effects | mRNA vaccines can cause side effects such as pain, redness, or swelling at the injection site, as well as tiredness, headache, muscle pain, chills, fever, or nausea. Rare but serious side effects include anaphylaxis, pericarditis, and myocarditis. |
| Comparison | Traditional vaccines may use weakened or inactivated viruses or parts of the virus, unlike mRNA vaccines, which do not contain any live virus. |
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How mRNA vaccines work
Vaccines help prevent infection by preparing the body to fight foreign invaders (such as bacteria, viruses, or other pathogens). All vaccines introduce into the body a harmless piece of a particular bacteria or virus, triggering an immune response.
MRNA vaccines work by introducing a piece of mRNA that corresponds to a viral protein, usually a small piece of a protein found on the virus's outer membrane. This mRNA directs cells to produce copies of a protein on the outside of the coronavirus known as the "spike protein".
By injecting cells with a synthetic mRNA that encodes a viral spike protein, an mRNA vaccine can direct human cells to make a viral spike protein and evoke an immune response without a person ever having been exposed to the viral material. These viral spike proteins, or antigens, normally coat the surface of the virus and are recognized by antibodies and other immune cells that prepare and protect the body against the virus. If a person is later exposed to the virus, antibodies and other parts of the immune system can recognize and attack the virus before it can infect healthy cells or cause illness.
MRNA acts as a cellular messenger. DNA, which is stored in a cell's nucleus, encodes the genetic information for making proteins. mRNA transfers a copy of this genetic information outside of the nucleus, to a cell's cytoplasm, where it is translated into amino acids by ribosomes and then folded into complete proteins. Once cells finish making a protein, they quickly break down the mRNA, which leaves the body as waste.
MRNA vaccines have been studied before for flu, Zika, rabies, and cytomegalovirus (CMV). Beyond vaccines, cancer research has also used mRNA to trigger the immune system to target specific cancer cells.
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How non-mRNA vaccines work
Unlike mRNA vaccines, non-mRNA vaccines use a weakened or inactivated form of a virus or bacterium to trigger an immune response. This approach, which involves introducing a deactivated, or "killed", virus or bacterium, is more traditional and has been used for decades.
Non-mRNA vaccines introduce a weakened or dead bacteria or virus into the body, triggering an immune response. This immune response is the body's way of preparing to fight foreign invaders such as bacteria, viruses, or other pathogens.
The Novavax vaccine, for example, is a non-mRNA vaccine that contains the spike protein of the coronavirus itself. However, it is formulated as a nanoparticle, which cannot cause disease. When injected, this vaccine stimulates the immune system to produce antibodies and T-cell immune responses.
Another example of a non-mRNA vaccine is the protein subunit vaccine, which contains pieces (proteins) of the virus that causes COVID-19. These vaccines also contain an adjuvant, an ingredient that helps the immune system respond to the spike protein. Once the immune system knows how to respond to the spike protein, it can quickly react to the actual virus spike protein and protect against COVID-19.
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Safety
The safety profile of mRNA vaccines is a key area of focus in their development and deployment. mRNA vaccines are generally considered safe due to their transient expression and non-integrative nature inside host cells. They do not enter the nucleus, which contains DNA, and therefore pose no concern for DNA integration. This differentiates them from live-attenuated or viral-vectored vaccines, which use a weakened or modified version of a virus, and inactivated vaccines, which use a killed version of the virus.
MRNA vaccines are also non-infectious, as they do not contain any live microbes, and cannot give a person an infection. This is in contrast to live vaccines, which may not be suitable for people with weakened immune systems due to the presence of a small amount of live virus.
However, no vaccine is without risks, and mRNA vaccines are associated with certain side effects and adverse events, including, in rare cases, mortality. The most common local side effects of mRNA vaccines are redness, swelling, heat, and pain at the injection site. Other possible side effects include flu-like symptoms, and, in rare cases, myocarditis and pericarditis, particularly in male adolescents and young adults. Anaphylaxis, a severe allergic reaction, has also been reported, though this is rare.
It is important to note that all vaccines must pass rigorous safety testing before being administered to the general public, and the safety data for mRNA vaccines specifically indicates a favourable profile compared to other vaccines.
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Efficacy
MRNA vaccines are a relatively new type of vaccine. They contain genetic material that tells the body how to make a protein that will cause an immune response. This immune response teaches the body how to protect itself from a specific virus. For example, the SARS-CoV-2 virus has spike proteins on its surface. mRNA vaccines tell the body how to make these spike proteins, which then stimulate an immune response.
MRNA vaccines have several advantages over non-mRNA vaccines. They have a shorter manufacturing time, are inexpensive, and are rapidly developed. They are also safe due to their transient expression and non-integrative nature inside the host cells. They cannot give a person an infection or change a person's DNA.
However, mRNA vaccines can cause side effects in the days after a person receives them. These side effects include a sore arm, redness, swelling, heat, pain, and flu-like symptoms. More severe but rare side effects include pericarditis, myocarditis, and anaphylaxis.
Non-mRNA vaccines work in a different way, depending on the type of vaccine. Live vaccines use a weakened form of a microbe that causes an infection, while inactivated vaccines use dead microbes. Non-mRNA vaccines can provide strong and lasting protection against future infections, and in some cases, lifelong immunity.
One example of a non-mRNA COVID-19 vaccine is Novavax, which has about the same efficacy as other COVID vaccines. Novavax relies on a more traditional approach in which proteins resembling those in SARS-CoV-2 are injected directly into the body. This protein-based method has been used for more than 30 years in other vaccines, such as the hepatitis B vaccine.
Novavax has been shown to have a lower risk of causing myocarditis or pericarditis compared to mRNA vaccines. However, it is difficult to directly compare the efficacy of different vaccines as there are many factors that can influence their effectiveness, such as previous infections and combinations of vaccinations.
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Production
MRNA vaccines have the potential for rapid, inexpensive, and scalable manufacturing. This is due to the high yields of in vitro transcription reactions. The development of mRNA vaccines can be much faster than traditional vaccines, which often take years or even a decade to produce. The speed of mRNA vaccine development was particularly important during the COVID-19 pandemic, where the Pfizer/BioNTech and Moderna vaccines were successfully created and deployed.
MRNA vaccines can be quickly designed and scaled up, and they do not require the same chemicals and cell cultures as non-mRNA vaccines. mRNA is made through a cell-independent process, and it does not need to be inactivated, reducing safety concerns related to contamination.
MRNA vaccines are also versatile. They can be rapidly tailored to different diseases or variants, making them suitable for future health emergencies. This versatility also means they can be personalised to target specific conditions in individual patients, such as cancer.
However, it is important to note that mRNA vaccines have faced challenges related to instability and delivery issues, which have been recent areas of focus for researchers.
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Frequently asked questions
mRNA vaccines are a type of vaccine that contains genetic material, or mRNA, that tells the body how to make a protein. This protein triggers an immune response, teaching the body how to protect itself from a specific virus.
Non-mRNA vaccines, also known as traditional vaccines, work differently depending on the type of vaccine. Live vaccines use a weakened form of a virus to trigger an immune response, while inactivated vaccines use dead microbes.
mRNA vaccines teach our cells to make a spike protein, which is found on the surface of the virus that causes COVID-19. Our immune system recognises that the protein does not belong there and produces antibodies to fight off what it thinks is an infection. This process teaches our bodies to protect against future infection with the virus.
