Find answers to questions about COVID-19 vaccines, dispel misconceptions, and fact check misinformation.

Frequently Asked Questions

Why does it matter if I get the COVID-19 vaccine or not?

It matters because the vaccine can help protect you and those around you. The vaccine will add extra protection. COVID-19 vaccines are effective and can lower your risk of getting and spreading the virus that causes COVID-19. COVID-19 vaccines also help prevent serious illness and death in children and adults, even if they do get COVID-19. (Source: cdc.gov/coronavirus)

Do I need to get the vaccine if I already had COVID-19?

Yes, you should still get vaccinated if you already had COVID-19. Data shows it is uncommon to be re-infected with COVID-19 in the 90 days after you were infected. That means you might have some protection from COVID-19 (called natural immunity) for a little while. However, we don’t know how long natural immunity lasts. Learn more about why you should still get vaccinated with a COVID-19 vaccine.

Are the vaccines actually safe or effective?

Yes, the COVID-19 vaccines are safe and effective. Scientists tested the vaccines on tens of thousands of participants in clinical trials. The vaccines met the U.S. Food and Drug Administration’s (FDA) standards for safety, effectiveness, and manufacturing quality needed to get emergency use authorization. They were all found to be very good at preventing people from getting sick with COVID-19. Since then, these vaccines have been given safely to millions of people.

Do I need the COVID-19 vaccine, or can I just use herbal remedies and supplements instead?

Many people take vitamin C, zinc, green tea, or echinacea to boost their immune systems. However, these supplements are unlikely to affect your immune function or prevent you from getting sick with COVID-19. Colloidal silver, which has been falsely marketed as a COVID-19 treatment, is not safe or effective for treating any disease. Oleandrin, an extract from the toxic oleander plant, is poisonous and shouldn’t be taken as a supplement or home remedy. (Source: Mayo Clinic)

Could I get a blood clot from the vaccine?

The risk of getting blood clots is extremely low. The number of people who got blood clots after the Johnson & Johnson vaccine was very low compared to the millions of people who got vaccinated and didn’t get blood clots. However, DOH and CDC recommend people 18 years and older choose to get an mRNA COVID-19 vaccine (Pfizer or Moderna) instead of the Johnson & Johnson vaccine due to the potential risk of thrombosis with thrombocytopenia syndrome (TTS), which involves blood clots and a low platelet count, and Guillain-Barré syndrome, which is an autoimmune disorder that can cause nerve damage.

The Johnson & Johnson vaccine is still available if you aren’t able or willing to get an mRNA vaccine. You can talk to your health care provider about your risk. Most reports of blood clots after the Johnson & Johnson vaccine were in adult women younger than 50 years old. If you are a woman between 18 and 50 years old, you should be aware that you have a higher risk of getting blood clots, which could lead to death. The blood clot concern was only associated with the Johnson & Johnson COVID-19 vaccine, not the Pfizer or Moderna vaccines.

Learn more by reading about the Johnson & Johnson Vaccine and Blood Clots: What You Need to Know. You can also watch this video from Dr. Paul Offit discussing the blood clotting condition a few people have experienced after getting the Johnson & Johnson COVID-19 vaccine and what is known about the risk for individuals.

What ingredients are in the vaccine?

You may see some rumors and untrue ingredients listed online or on 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 complete ingredients lists in the Pfizer, Moderna, and Johnson & Johnson fact sheets.

Does the vaccine contain the live virus?

None of the COVID-19 vaccines contain a live virus. One of the COVID-19 vaccines authorized by the FDA is a viral vector vaccine (Johnson & Johnson). Viral vector vaccines contain a killed version of a virus—a different virus than the one that causes COVID-19—that teaches your cells to make a harmless piece of the coronavirus spike protein. Your immune system sees that the protein shouldn’t be there, which triggers your body to produce antibodies that remember how to fight that virus if you are infected with COVID-19 in the future.

What is messenger RNA (mRNA)?

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 COVID-19.

The vaccine seemed to happen overnight. How can I trust the vaccines are safe?

The COVID-19 pandemic impacts everyone in the United States – our health, the health of families and communities, and our economic system. Health officials across the country are tackling this pandemic aggressively and ensuring the safety of vaccines because it impacts everyone.

It’s important for us, as a health department, to acknowledge that many members of Black, Indigenous, and other communities of color (BIPOC communities) worry about the safety of the COVID-19 vaccine because of the history of harmful and racist practices in science and health care. We cannot ignore this history and rightful distrust, and we must move forward with transparency.

Scientists and public health are sharing everything we know about the vaccine, including when we have concerns. We know the COVID-19 vaccines are safe and effective, and they give you protection against getting very sick with COVID-19. Learn more about COVID-19 vaccine equity.

What are the three types of COVID-19 vaccines?

Messenger RNA (mRNA) Vaccine: This type of vaccine uses genetically engineered mRNA to give your cells instructions for how to make a harmless piece of the S protein found on the surface of the COVID-19 virus. After vaccination, your immune cells begin making the S protein pieces and displaying them on cell surfaces. This causes your body to create antibodies. If you become infected with the COVID-19 virus, these antibodies will fight the virus.

Viral Vector Vaccine: This type of vaccine contains a modified version of a different virus than the one that causes COVID-19. Inside the shell of the modified virus, there is material from the virus that causes COVID-19. This is called a “viral vector.” Once the viral vector is inside our cells, the genetic material gives cells instructions to make a protein that is unique to the virus that causes COVID-19. Using these instructions, our cells make copies of the protein. This prompts our bodies to build T-lymphocytes and B-lymphocytes that will remember how to fight that virus if we are infected in the future.

Protein Subunit Vaccine: Subunit vaccines include only the parts of a virus that best stimulate your immune system. This type of COVID-19 vaccine contains harmless S proteins. Once your immune system recognizes the S proteins, it creates antibodies and defensive white blood cells. If you become infected with the COVID-19 virus, the antibodies will fight the virus. Novavax is working on a protein subunit COVID-19 vaccine.

Why do I need two shots for a specific vaccine and only one for another?

When a vaccine requires two shots, the first shot helps your body recognize the virus and gets your immune system ready, while the second shot strengthens that immune response. This makes your body more prepared to fight infection.

After getting the first shot, it can take up to a few weeks for your body to develop the cells that will make you immune. This means that it’s possible for you to get sick (infected) during that time. So it’s important to continue wearing masks and practicing social distancing even after getting the vaccine.

The available data continues to support the use of two doses of the Pfizer and Moderna vaccines. For Pfizer, the interval is 21 days between the first and second dose. And for Moderna, the interval is 28 days between the first and second dose. (Source: FDA.gov) The Johnson & Johnson vaccine is only one dose.

For all three vaccines, a booster shot is highly encouraged for maximum protection. For Pfizer and Moderna, you can get a booster 5 months after your second dose. For Johnson & Johnson, it’s 2 months after your initial dose. An mRNA COVID-19 vaccine (Moderna or Pfizer) is preferred for both primary and booster doses.

Do the vaccines cause long-term side effects?

We have a lot of scientific data on vaccines for COVID-19 and other diseases. Based on that data, experts are confident that these vaccines are very safe. Almost all reactions to the COVID-19 vaccine have been mild, like fatigue or a sore arm, and only last a couple of days. Serious or long-term reactions are extremely rare.

Any long-term side effects usually happen within eight weeks of vaccination. This is why the vaccine manufacturers were required to wait at least eight weeks after clinical trials before they could apply for Emergency Use Authorization from the U.S. Food and Drug Administration (FDA). Experts are also continuing to monitor COVID-19 vaccines for safety concerns. The FDA investigates any reports of serious side effects or reactions. Learn more about what we know so far about long-term side effects of COVID-19 vaccines.

Will the vaccine change my DNA?

No, the COVID-19 vaccines do not change or alter your DNA. The vaccines deliver instructions to our cells to start building protection against the virus that causes COVID-19. The vaccine does not enter the part of the cell where our DNA is kept. Instead, the vaccines work with our body’s natural defenses to build immunity. Learn more about mRNA and viral vector COVID-19 vaccines.

Will I be able to have children if I get the COVID-19 vaccine?

Yes. Your worries around reproductive health and vaccines are understandable. Here is what we know: there is no scientific evidence that vaccines cause infertility or impotence. When the vaccine enters your body, it works with your immune system to create antibodies to fight the coronavirus. This process does not interfere with your reproductive organs.

The American College of Obstetricians and Gynecologists (ACOG) recommends the COVID-19 vaccine to anyone who may want to get pregnant in the future or is currently pregnant or breastfeeding. Many people who have gotten vaccinated against COVID-19 have since gotten pregnant or given birth to healthy babies.

See Coronavirus (COVID-19), Pregnancy, and Breastfeeding: A Message for Patients for more information. You can also see the U.S. Food and Drug Administration (FDA) COVID-19 Vaccines webpage for facts about the vaccines.

Is the vaccine safe for people who are pregnant?

Yes, you can get vaccinated if you are pregnant, and the American College of Obstetricians and Gynecologists (ACOG) recommends the vaccine for pregnant people. There is no evidence that the COVID-19 vaccine causes any problems with pregnancy, the development of your baby, birth, or fertility.

In the Pfizer vaccine trials, 23 volunteers became pregnant. One participant suffered a pregnancy loss, but this participant received a placebo, not the actual vaccine. Getting COVID-19, on the other hand, can have a potentially serious impact on your pregnancy and health. The vaccine is your best protection against COVID-19.

Does the vaccine affect the menstrual cycle?

Some people have reported changes in their menstrual cycles after getting vaccinated, but there is no data currently available to suggest these are long-term effects. Menstrual cycles can change due to many different things, like stress. Learn more about the truth behind COVID-19 and women’s health.

Is the vaccine safe for people who are breastfeeding?

Yes, you can get vaccinated if you are breastfeeding. You do not need to stop breastfeeding if you want to get vaccinated. In fact, early reports suggest the vaccine might help your body pass antibodies to your baby through breastmilk. More studies are needed, but if this is confirmed, it will help protect your baby from COVID-19.

Read more about how the COVID-19 vaccine protects mothers and their newborns.

Should I be more worried about taking the vaccine than getting COVID-19?

Taking the vaccine is by far the safer choice. The risk of serious outcome from getting COVID-19 disease far outweigh any of the very rare risks from getting the vaccine. If you are concerned about having a bad reaction to the vaccine, discuss it with your doctor, nurse, or clinic, and they’ll advise what is right for you.

I keep hearing "what we know about the vaccine," but can you tell me what we DON'T know about the vaccine?

While these vaccines are the newest we have, the science behind them is not new. And we have been vaccinating people for over 200 years, so we know a lot about how the process works. We know the vaccines so far have been safe and effective. They are also some of the most studied vaccines we’ve ever produced, so we know a lot about them. Typically, with vaccines, any bad side effect happens within a few days to a few weeks, and so far, the COVID-19 vaccines have been the same, so we do not expect to learn about any more risks than we already know about. However, the United States and other countries have very robust safety systems in place to catch any new issue that may come up, and scientists work quickly to correct or remove any vaccine that has a concerning risk.

Were Black and African American people a part of the vaccine development process and trials?

Yes. Ten percent of the Pfizer and Moderna vaccine trial participants were Black/African American (about 7,000 people). Among the J&J study participants, six percent were Black/African American.

What are COVID variants, and why do they keep popping up?

Viruses can mutate (change) as they spread from person to person. A ‘variant’ is a mutated strain of the virus. Some variants disappear over time, and some continue to spread in communities. Some are not as effective at causing disease, and others are more effective. The more effective variants can cause concern. The Centers for Disease Control and Prevention (CDC) identifies variants that are concerning. A variant is considered concerning if it spreads quickly and more easily, causing more COVID-19 infections.

Getting vaccinated helps slow the spread of the virus and helps protect you from serious illness, hospitalization, and death from COVID-19. Some vaccinated people may still get infected with a variant strain, but research shows they tend to experience mild symptoms. It’s important to get all recommended doses, so you have maximum protection against variants.

What is in the booster shot, and why so soon?

COVID-19 booster shots are the same ingredients (formulation) as the current COVID-19 vaccines. However, in the case of the Moderna COVID-19 vaccine booster shot, the dose is half of the amount of the vaccine people get for their primary series.

The COVID-19 vaccines authorized or approved in the United States are still very effective at reducing the risk of severe disease, hospitalization, and death from COVID-19, even against variants. Still, the current vaccines may be associated with a drop in protection over time. Booster doses will increase vaccine-induced protection against COVID-19 and help immunity last longer. This is similar to how you need a tetanus booster every 10 years to keep up your vaccine protection against that disease.

Do I need a booster, and how often will I need to get one?

The CDC and the Western States Scientific Safety Review Workgroup recommend everyone 12 years and older who received the Johnson & Johnson, Pfizer, or Moderna COVID-19 vaccine primary series to get a booster dose. Currently, you are eligible for a booster dose 5 months after you finish the primary series of the Moderna or Pfizer vaccine or 2 months after receiving the Johnson & Johnson vaccine. It’s possible that more boosters may be needed in the future, not unlike other vaccines, such as for the flu.

Is the vaccine safe for my child?

Yes. The Pfizer vaccine was tested on thousands of youths and shown to be safe. It was also very effective – none of the youth volunteers who got the vaccine got COVID-19. The Centers for Disease Control and Prevention (CDC) recommends the COVID-19 vaccine to everyone 5 years and older.

Dr. John Vassall MD, FACP:

Why We Can Trust the COVID-19 Vaccine

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