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This type of vaccine uses a weakened version of a different virus (the “vector”) that gives your cells instructions. The vector enters a cell and uses the cell’s machinery to create a harmless piece of the COVID-19 spike protein. The cell displays the spike protein on its surface, and your immune system sees that it doesn’t belong there. Your immune system will start to make antibodies and activate other immune cells to fight off what it thinks is an infection. Your body learns how to protect you against future infection with COVID-19, without you having to get sick.
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This short video explains how COVID vaccines are made
The COVID-19 vaccine teaches your immune system to recognize the coronavirus. When you get the vaccine, your immune system makes antibodies (“fighter cells”) that stay in your blood and protect you in case you are infected with the virus. You get protection against the disease without having to get sick.
When enough people in the community can fight off the coronavirus, it has nowhere to go. This means we can stop the spread quicker and get a little closer to ending this pandemic.
You may see some rumors and untrue ingredients listed online or in social media. These are generally myths. The ingredients in the COVID-19 vaccines are pretty typical for vaccines. They contain the active ingredient of mRNA or modified adenovirus along with other ingredients like fat, salts, and sugars that protect the active ingredient, help it work better in the body, and protect the vaccine during storage and transport.
See this Q&A webpage from the Children’s Hospital of Philadelphia for more information about ingredients. You can also find the full ingredients lists in the Pfizer, Moderna, and Johnson & Johnson fact sheets.
A messenger RNA, or mRNA vaccine is a new type of vaccine. mRNA vaccines teach your cells how to make a harmless piece of the “spike protein.” The spike protein is what you see on the surface of the coronavirus. Your immune system sees that the protein doesn’t belong there and your body will start to build an immune response and make antibodies. This is similar to what happens when we “naturally” get a COVID-19 infection.
Although we have used mRNA for other types of medical and veterinary care in the past, creating vaccines using this method is a huge leap forward in science and may mean future vaccines can be created more easily.
You may read more about how mRNA vaccines work on CDC’s website, or watch this video from Dr. Paul Offit at the Children’s Hospital of Philadelphia.
Like other routine vaccines, the most common side effects are a sore arm, fatigue, headache, and muscle pain.
These symptoms are a sign that the vaccine is working. In the Pfizer and Moderna trials, these side effects occurred most often within two days of getting the vaccine, and lasted about a day. Side effects were more common after the second dose than the first dose. In the Johnson & Johnson clinical trials, side effects lasted an average of one to two days.
For all three vaccines, people over 55 were less likely to report side effects than younger people.
Clinical trials found that approximately:
You may see some rumors about untrue side effects online or on social media. Make sure any time you see a claim about a side effect that you check the source of that claim. This video can teach you more about how to figure out if a claim online is true or not.
The vaccine should not be given to people with a known history of severe allergic reaction, such as anaphylaxis, to a previous dose of an mRNA or viral vector vaccine, or to any ingredient of the Pfizer-BioNTech, Moderna, or Johnson & Johnson–Janssen COVID-19 vaccines.
People who have had a severe allergic reaction to other vaccines or injectable therapies may still be able to receive the vaccine. However, providers should do a risk assessment and counsel them about potential risks. If the patient decides to get the vaccine, the provider should observe them for 30 minutes to monitor for any immediate reactions.
The Advisory Committee on Immunization Practices (ACIP) recommends that providers observe all other patients for at least 15 minutes after receiving the vaccine to monitor for an allergic reaction. See ACIP’s interim clinical considerations for mRNA vaccines for more information.
Yes. People who are pregnant, lactating, or planning to become pregnant may choose to get the vaccine any time.
The American College of Obstetricians and Gynecologists (ACOG) and the Centers for Disease Control and Prevention (CDC) recommend you talk with your health care provider about whether the vaccine is right for you. While safety data on the use of COVID-19 vaccine in pregnant people is limited, the information we have is reassuring.
If you would like to speak to someone about getting the COVID-19 vaccine during pregnancy, please contact MotherToBaby. MotherToBaby experts are available to answer questions in English or Spanish by phone or chat. The free and confidential service is available Monday to Friday 8 a.m. to 5 p.m. (local time). To reach MotherToBaby: