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It can be difficult to know which sources of information you can trust. Learn more about finding credible vaccine information.
No. None of the authorized and recommended COVID-19 vaccines or COVID-19 vaccines currently in development in the United States contain the live virus that causes COVID-19. This means that a COVID-19 vaccine cannot make you sick with COVID-19.
There are several different types of vaccines in development. All of them teach our immune systems how to recognize and fight the virus that causes COVID-19. Sometimes this process can cause symptoms, such as fever. These symptoms are normal and are a sign that the body is building protection against the virus that causes COVID-19. Learn more about how COVID-19 vaccines work.
It typically takes a few weeks for the body to build immunity (protection against the virus that causes COVID-19) after vaccination. That means it’s possible a person could be infected with the virus that causes COVID-19 just before or just after vaccination and still get sick. This is because the vaccine has not had enough time to provide protection.
Yes. COVID-19 vaccination works by teaching your immune system how to recognize and fight the virus that causes COVID-19, and this protects you from getting sick with COVID-19.
Being protected from getting sick is important because even though many people with COVID-19 have only a mild illness, others may get a severe illness, have long-term health effects, or even die. There is no way to know how COVID-19 will affect you, even if you don’t have an increased risk of developing severe complications. Learn more about how COVID-19 vaccines work.
No. COVID-19 vaccines do not change or interact with your DNA in any way.
There are currently two types of COVID-19 vaccines that have been authorized for use in the United States: messenger RNA (mRNA) vaccines and viral vector vaccines.
The Pfizer-BioNTech and Moderna vaccines are mRNA vaccines, which teach our cells how to make a protein that triggers an immune response. The mRNA from a COVID-19 vaccine never enters the nucleus of the cell, which is where our DNA is kept. This means the mRNA cannot affect or interact with our DNA in any way. Instead, COVID-19 mRNA vaccines work with the body’s natural defenses to safely develop immunity to disease. Learn more about how COVID-19 mRNA vaccines work.
Johnson & Johnson’s Janssen COVID-19 vaccine is a viral vector vaccine. Viral vector vaccines use a modified version of a different, harmless virus (the vector) to deliver important instructions to our cells to start building protection. The instructions are delivered in the form of genetic material. This material does not integrate into a person’s DNA. These instructions tell the cell to produce a harmless piece of virus that causes COVID-19. This is a spike protein and is only found on the surface of the virus that causes COVID-19. This triggers our immune system to recognize the virus that causes COVID-19 and to begin producing antibodies and activating other immune cells to fight off what it thinks is an infection. Learn more about how viral vector vaccines work.
At the end of the process, our bodies have learned how to protect against future infection from COVID-19. That immune response and the antibodies that our bodies make protect us from getting infected if the real virus enters our bodies.
People with underlying medical conditions can receive the FDA-authorized COVID-19 vaccines as long as they have not had an immediate or severe allergic reaction to a COVID-19 vaccine or to any of the ingredients in the vaccine. Learn more about vaccination considerations for people with underlying medical conditions. Vaccination is an important consideration for adults of any age with certain underlying medical conditions because they are at increased risk for severe illness from COVID-19.
Yes, you should be vaccinated regardless of whether you already had COVID-19. That’s because experts do not yet know how long you are protected from getting sick again after recovering from COVID-19. Even if you have already recovered from COVID-19, it is possible—although rare—that you could be infected with the virus that causes COVID-19 again. Learn more about why getting vaccinated is a safer way to build protection than getting infected.
If you were treated for COVID-19 with monoclonal antibodies or convalescent plasma, you should wait 90 days before getting a COVID-19 vaccine. Talk to your doctor if you are unsure what treatments you received or if you have more questions about getting a COVID-19 vaccine.
Experts are still learning more about how long vaccines protect against COVID-19 in real-world conditions. CDC will keep the public informed as new evidence becomes available.
The ingredients in currently available COVID-19 vaccines include mRNA, lipids, salts, sugars, and buffers. Buffers help maintain the stability of the pH solution. Vaccine ingredients can vary by manufacturer. To learn more about the ingredients in authorized COVID-19 vaccines, see
The federal government is providing the vaccine free of charge to all people living in the United States. Vaccination providers can be reimbursed for vaccine administration fees by the patient’s public or private insurance company or, for uninsured patients, by the Health Resources and Services Administration’s Provider Relief Fund. No one can be denied a vaccine if they are unable to pay a vaccine administration fee.
No. Neither the recently authorized and recommended vaccines nor the other COVID-19 vaccines currently in clinical trials in the United States can cause you to test positive on viral tests, which are used to see if you have a current infection.
If your body develops an immune response—the goal of vaccination—there is a possibility you may test positive on some antibody tests. Antibody tests indicate you had a previous infection and that you may have some level of protection against the virus. Experts are currently looking at how COVID-19 vaccination may affect antibody testing results.
No. People with COVID-19 who have symptoms should wait to be vaccinated until they have recovered from their illness and have met the criteria for discontinuing isolation; those without symptoms should also wait until they meet the criteria before getting vaccinated. This guidance also applies to people who get COVID-19 before getting their second dose of vaccine.
We don’t know how long protection lasts for those who are vaccinated. What we do know is that COVID-19 has caused very serious illness and death for a lot of people. If you get COVID-19, you also risk giving it to loved ones who may get very sick. Getting a COVID-19 vaccine is a safer choice.
Experts are working to learn more about both natural immunity and vaccine-induced immunity. CDC will keep the public informed as new evidence becomes available.
Yes. If you are trying to become pregnant now or want to get pregnant in the future, you may receive a COVID-19 vaccine when one is available to you.
There is currently no evidence that COVID-19 vaccination causes any problems with pregnancy, including the development of the placenta. In addition, there is no evidence that fertility problems are a side effect of any vaccine, including COVID-19 vaccines.
Like all vaccines, scientists are studying COVID-19 vaccines carefully for side effects now and will continue to study them for many years.