Health
Covid-19 Vaccine: How Do They Work?
Explore the various types of Covid-19 vaccines.
As Covid-19 vaccines become available, they will help prevent a disease that can be dangerous or even deadly. Today, we explore how our bodies fight infection and how Covid-19 vaccines work to protect us by producing immunity.
Our immune system: Our defense system against infection
Understanding how the new and innovative Covid-19 vaccines work will help explore how our bodies mount defenses against illness. First, what is an infection? When germs invade us, the microorganisms attack and multiply. Fortunately, our immune system has a wide range of tools to counter disease. For example, our bloodstream contains white blood cells. These white blood cells come in different varieties, helping you to fight infection in differing ways:
- Macrophages are white blood cells that eat and digest dead (or dying) cells. After doing so, the macrophages leave behind parts of the invading germs. We call these bits antigens. Our bodies recognize antigens as problematic and stimulate antibodies to attack them.
- B-lymphocytes are white blood cells that make antibodies to attack the virus's pieces left behind by the macrophages.
- T-lymphocytes attack cells in our body that have already been infected.
What happens if the Covid-19 virus infects you? After several days or weeks, the body will use all of the tools described above to get over the infection. Survive, and you will have a supply of “memory cells” (T-lymphocytes) that will know how to protect the body in the future. When the T-cells detect a future infection, the B-lymphocytes leap into action to produce antibodies to attack the foreign invaders. Let’s turn to the new vaccines.
Vaccine types
Today, we have three main types of Covid-19 vaccines that are in large scale studies in the United States.
- mRNA vaccines. These have material from the virus that causes Covid-19 infection. The bits of information give our cells guidance on making a harmless protein unique to the virus. Here’s how the process unfolds: Our cells make copies of the protein and then destroy the vaccine's genetic material. Our bodies recognize that the protein shouldn’t be there and build T- and B-lymphocytes that retain a memory or fight the virus that causes Covid-19 should we become infected in the future.
- Protein subunit vaccines. Instead of containing the entire germ, this approach incorporates harmless proteins of the virus that causes Covid-19. Our bodies recognize these proteins as foreign and create T-lymphocytes and antibodies. Now the cells have memory, and if we become infected in the future, they are ready for the fight.
- Vector vaccines. These have a weakened version of a live virus.
Moderna versus Pfizer vaccine
Now that we understand the basics of our immune system let’s turn to two vaccines. The Pfizer-BioNTech vaccine is shipping to Americans now. A second vaccine is in the wings, with the Moderna (did you notice the mRNA inside the company name?) coronavirus vaccine similar to the approved Pfizer one. They have different lipid delivery systems, meaning the fatty droplet in which the messenger RNA is placed. These mRNA vaccines are around 95 percent effective and appear to have excellent side effect profiles.
How do these vaccines differ?
The Moderna and Pfizer vaccines are remarkably similar. In the USA, we are likely to have a decision about the Moderna vaccine today. The pros of the Moderna approach? The Moderna vaccine can be stored in standard freezers. The Pfizer one requires super-cold transportation networks (minus-75 degrees Celsius, about 50 degrees colder than any vaccine currently used in the US). The vaccine expires after five days in the refrigerator. In contrast, the Moderna vaccine is kept at about minus-20 degrees Celsius or about a home freezer’s temperature. This vaccine can chill in the refrigerator for up to thirty days.
The Moderna vaccine is given in two doses 28 days apart. The Pfizer vaccine is also two doses, but 21 days apart. The Moderna vaccine is for those 18 and older, while the Pfizer vaccine has been authorized in the USA for those 16 and older.
The Moderna vaccine is given in two doses 28 days apart. The Pfizer vaccine is also two doses, but 21 days apart. The Moderna vaccine is for those 18 and older, while the Pfizer vaccine has been authorized in the USA for those 16 and older.
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