March Provider Newsletter

How does the COVID-19 vaccine work?

There are multiple COVID-19 vaccines being developed. They work in slightly different ways.

In the United States, there are a few COVID-19 vaccines available. All of these have been found to work very well in preventing serious illness and death from COVID-19. They include:

mRNA vaccines – The first 2 vaccines became available in late 2020, generally known as the “Pfizer” and the “Moderna” vaccinations. Both are a type of vaccine called an "messenger RNA vaccine or mRNA vaccine." mRNA refers to genetic material from the virus that causes COVID-19. This genetic material is used in the vaccine. It gives the body instructions to make a specific piece of protein that is normally found on the virus. In response, the immune system then makes antibodies that can recognize and attack the virus in the future.

The mRNA vaccines for COVID-19 require 2 doses given a few weeks apart. It's important to get both doses for the vaccine to be most effective. When to get the second dose depends on which vaccine you get. It is important to note that these vaccines do not change or alter your own DNA or genetic code in your cells in any way.


Vector vaccine – In early 2021, another type of vaccine became available. This is called a "vector vaccine," generally known as the one shot “Johnson and Johnson” vaccination. It contains a weakened version of a different virus, called an adenovirus. This virus does not make you sick, but it acts as a "vector," or a way to deliver instructions to all the cells in your body. These instructions tell your body to make the protein normally found on the virus that causes COVID-19. Then, your immune system makes antibodies that can recognize and attack the virus in the future.

The vector vaccine only requires one dose.


It's important to know that these COVID-19 vaccines do not contain infectious SARS-CoV-2 virus, so they cannot give you COVID-19. They also do not affect your DNA.

Different COVID-19 vaccines are available in other countries.

Do vaccines work against the different virus variants?

Viruses constantly change or "mutate." When this happens, a new strain or "variant" can form. Most of the time, new variants do not change the way a virus works. But when a variant has changes in important parts of the virus, it can act differently.

Experts have discovered several new variants of the virus that causes COVID-19. They are studying them to better understand if and how they act differently. They are also studying how well the available vaccines work to protect against them. From what they know so far, it seems like the available vaccines provide at least some protection from the different variants.

Does the COVID-19 vaccine cause side effects?

It can. Side effects are common, especially after the second dose of the vaccines that come in two doses. They can include:

Pain where you got the shot (upper arm)


Feeling very tired


Many people (including myself) had some achiness in the arm at the site of injection. It was very similar to my experience of getting a seasonal influenza vaccination. While these side effects can be annoying, they should not last longer than a day or two. They do not mean you are sick, just that your immune system is responding to the vaccine.

Vaccines also sometimes cause more serious side effects, such as severe allergic reactions. But this is rare. If you have had a reaction to the vaccine or its ingredients in the past, you might need to talk to an allergy expert. They can help you figure out if you should get the COVID-19 vaccine. People who do get the vaccine might be monitored for 15 or so minutes to make sure they do not have an allergic reaction.

Can I get COVID-19 from the vaccine?

No. You cannot get COVID-19 from the vaccine.

Some people worry that the vaccine actually contains the virus that causes COVID-19. The vector vaccine that is available in the United States does contain virus, but it is a different virus. It is also created in a lab in a weakened form so it will not make a healthy person sick. mRNA vaccines do not contain virus at all.

Why should I get the COVID-19 vaccine?

Getting vaccinated lowers your chances of getting sick. If you do get COVID-19, the vaccine will probably also keep you from getting severely ill.

The virus that causes COVID-19 spreads very easily. In addition to protecting you, getting the vaccine will also help protect other people, including those who are at higher risk of getting very sick or dying. Even if you are not worried about getting very sick yourself, you could still spread the virus to others, even without realizing it.

When a lot of people have been vaccinated, the virus will stop spreading so quickly. This will allow everyone to get back to normal life sooner. But it only works if enough people get the vaccine.

How do I know the vaccine is safe?


COVID-19 vaccines have been developed by many teams of scientists working together, which led to a faster development than we typically see with most vaccinations. Because of this, some people wonder if they are safe. The answer is yes, the new vaccines had to go through the same process as other vaccines to test them for safety. This involved running "clinical trials" with lots of people who volunteered to try the vaccine. The volunteers included adults of all ages and ethnicities. During these trials, researchers studied how well the vaccines work and how many people had side effects. The results were reviewed by doctors and other experts who do not work for the drug companies that made the vaccines. These experts agreed that the vaccines are safe and effective enough to be given to the public.

It's true that clinical trials for the new COVID-19 vaccines have happened much more quickly than usual. That's because experts know that an effective vaccine will be one of the best ways to control the pandemic. In the United States, drug companies were able to work faster to develop vaccines because they received money from the government. This allowed them to focus their efforts on COVID-19. Drug companies were also able to make progress quickly because they had already learned a lot from working on other vaccines. This includes studying other vaccines that work similarly to the ones made for COVID-19.

Even after people start getting vaccines, researchers will continue to study how they work. They will learn more about how long a person is protected after getting a vaccine, and how well vaccination is working to slow the spread of COVID-19.

Peter Swarr, MD Dr. Swarr grew up in the Finger Lakes Region of beautiful Upstate New York. He received a Bachelor’s degree in History from Haverford College near Philadelphia, PA and his medical degree from University of Vermont College of Medicine where he was elected to Alpha Omega Alpha, the medical honor society. He completed the combined Internal Medicine and Pediatrics residency program at Vanderbilt University Medical Center. Vanderbilt medical students awarded him the Housestaff Clinical Teaching Award in both 2002 and 2003, which is given to select Vanderbilt resident physicians “in recognition of excellence in the clinical education of medical students – who embody the attributes of a caring physician and have been an exceptional role model”. Dr. Swarr was a chief resident in Internal Medicine at Vanderbilt in 2003. Dr. Swarr is board certified by both the American Board of Internal Medicine and the American Board of Pediatrics. He is very happy to have joined Cool Springs Internal Medicine & Pediatrics in 2004.

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