Frequently Asked Questions about COVID-19 Vaccines

The following information addresses frequently asked questions about COVID-19 vaccines. Although there are differences between the vaccines authorized for use in the US, all currently approved vaccines have the following in common:

  • All are nearly 100 percent effective in preventing hospitalization and death
  • All are not currently approved for use in children, but studies are ongoing
  • None contain the live virus or any component of the virus that causes COVID-19

Information about COVID-19 vaccines is changing rapidly. View the latest information on COVID-19 vaccination from the Centers for Disease Control and Prevention (CDC).

  • COVID-19 vaccination is recommended for everyone age 12 years and older, including pregnant or breastfeeding individuals.
  • CDC recommends that those individuals with immune systems that are moderately to severely compromised should receive an additional dose of mRNA COVID-19 vaccine after the initial two doses.

COVID-19 Vaccines Cannot Cause Disease


About the Vaccines

Who should be vaccinated against COVID-19?

In the US, COVID-19 vaccination is recommended for everyone age 12 years and older.  Contact your local health department for more information about COVID-19 vaccines available in your local area.

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Which COVID-19 vaccines are available in the US?

Three vaccines are currently available in the US. On August 23, 2021, FDA approved the Pfizer-BioNTech vaccine (now marketed as COMIRNATY®) for the prevention of COVID-19 disease in individuals age 16 years and older. The vaccine also continues to be available under emergency use authorization (EUA) for children age 12-15 years and for the administration of a third dose in certain immunocompromised individuals.

The Moderna and J&J/Janssen vaccines have received emergency use authorization from FDA and are recommended for individuals age 18 years and older.

Individuals may receive any age-appropriate COVID-19 vaccine and are encouraged to get vaccinated as soon as possible.

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What is an mRNA vaccine? Do mRNA vaccines affect DNA?

The vaccines from Pfizer and Moderna are messenger RNA (mRNA) vaccines. mRNA is found in all living cells, and mRNA vaccines work by teaching cells how to make a protein or a piece of a protein that triggers an immune response inside the body. That immune response, which produces antibodies, is what protects against infection if you are exposed to the virus.

mRNA is not the same as DNA, and it cannot combine with our DNA to change our genetic code. It is also relatively fragile, and will only hang around inside a cell for about 72 hours, before being degraded. mRNA vaccines do not affect or interact with DNA in any way. mRNA never enters the nucleus of the cell, which is where DNA (genetic material) is stored.

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Who should receive additional doses of COVID-19 vaccine?

CDC now recommends that adults age 65 years and older, residents in long-term care settings, and adults age 50–64 years with certain underlying medical conditions should receive a booster shot of a Pfizer-BioNTech COVID-19 vaccine at least 6 months after completing their Pfizer-BioNTech primary series. Other groups may receive a booster shot based on their individual risk and benefit. Read CDC media statement on booster recommendations to learn more.

Talk to a healthcare professional about your medical condition, and whether getting an additional dose is appropriate for you.

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When will vaccines be available for children?

Because children were not included in the initial clinical trials, the vaccines are not currently recommended for children younger than 12 years of age. Clinical trials in younger children are underway, and presuming the trials are successful, vaccine recommendations for younger children will be made once the trials are completed.

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How long are the vaccines effective? Will I need to be revaccinated each year?

Scientists do not yet know how long the protection from the COVID-19 vaccines will last. Scientists and public health experts are closely monitoring vaccine effectiveness and safety, and new information will be shared by the Centers for Disease Control and Prevention (CDC) as it becomes available.

Some vaccines provide life-long protection, such as the measles vaccine. Others require booster doses. For influenza (flu), everyone age 6 months and older should get vaccinated each year.

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Will COVID-19 vaccines work against new mutations of COVID-19?

Viruses constantly mutate, and public health experts expect new variants of a virus to occur. Multiple variants of SARS-CoV-2 (the virus that causes COVID-19) have been documented in the US and globally. The US government has developed a Variant Classification scheme that defines three classes of SARS-CoV-2 variants:

  • Variant of Interest (VOI)
  • Variant of Concern (VOC)
  • Variant of High Consequence (VOHC)

The Alpha (B.1.1.7), Beta (B.1.351, B.1.351.2, B.1.351.3), Delta (B.1.617.2, AY.1, AY.2, AY.3), and Gamma (P.1, P.1.1, P.1.2) variants circulating in the US are classified as Variants of Concern. To date, no Variants of High Consequence have been identified in the United States.

Scientists are monitoring changes in the virus, and information about these variants is rapidly emerging. The new variants seem to spread more easily and quickly, which may lead to more cases of COVID-19, but at this time, existing vaccines work well to prevent severe illness, hospitalization, and death.

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What other vaccines are being developed?

Globally, there are additional vaccine candidates in various stages of testing to evaluate their safety and effectiveness, including some that are based on proven technologies and some that use innovative approaches.

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Vaccine Safety

Are the vaccines safe?

All vaccines used in the US are required to go through extensive safety testing before they are licensed by the US Food and Drug Administration (FDA) or recommended for widespread use.

The new COVID-19 vaccines have been studied in multiple clinical trials, each of which has included thousands of individuals who were followed for a minimum of two months. Decades of experience with other vaccines indicate that the vast majority of adverse reactions occur within the first two months of vaccination.

Vaccinated individuals may have a sore arm, fatigue, headache, and even low-grade fever that lasts one or two days. This is to be expected, and it indicates that the vaccine is working.

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Should I be concerned about Guillain Barré syndrome (GBS) after COVID-19 vaccination?

There have been rare reports of Guillain Barré syndrome (a neurological disorder in which the immune system damages nerve cells, causing muscle weakness and sometimes paralysis) in some individuals who have received the J&J/Janssen COVID-19 vaccine. In most cases, symptoms began within 6 weeks of being vaccinated. According to FDA, the chance of occurrence is very low. If you have any of the following symptoms after receiving the  J&J/Janssen vaccine, seek medical care:

  • Weakness or tingling sensations, especially in the legs or arms, that is worsening and spreading to other parts of the body
  • Difficulty walking
  • Difficulty with facial movements, including speaking, chewing, or swallowing
  • Double vision or inability to move eyes
  • Difficulty with bladder control or bowel function

CDC and FDA are actively monitoring these reports and continue to recommend COVID-19 vaccination, as the benefits outweigh the risks.

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Should I be worried about myocarditis or pericarditis following COVID-19 vaccination?

There have been rare reports of inflammation of the heart (myocarditis or pericarditis) following vaccination with the mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna) in the US. Most of the reported cases have been among male adolescents and young adults and have occurred within several days following the second dose of the vaccine. Most patients with myocarditis and pericarditis who received care responded well to medicine and rest and quickly recovered.

If you have any of these symptoms within a week after COVID-19 vaccination, seek medical care:

• Chest pain
• Shortness of breath
• Feelings of having a fast-beating, fluttering, or pounding heart

CDC is actively monitoring these reports and continues to recommend COVID-19 vaccination for everyone age 12 years and older. The known and potential benefits of COVID-19 vaccination outweigh the known and potential risks.

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Are COVID-19 vaccines safe for people with allergies?

Individuals who have had severe allergic reactions to other vaccines or injectable therapies should not get vaccinated against COVID-19. People who have other allergies (e.g., allergies to food, animals, venom, environmental, or latex) may be vaccinated but should remain at the vaccination site for 15-30 minutes for observation. Individuals who carry epinephrine (EpiPen©) should bring it with them as a precaution.

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Are COVID-19 vaccines safe for people with liver disease, heart disease, or other chronic health conditions?

COVID-19 vaccines are safe and effective. Multiple studies show that older adults and those with certain medical conditions—like cancer, chronic kidney disease, chronic lung disease, dementia, diabetes (type 1 or type 2), down syndrome, heart disease, HIV, liver disease, and sickle cell disease—are at higher risk of severe illness or death from COVID-19.

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Is it safe to get a COVID-19 vaccine while pregnant or breastfeeding? Do COVID-19 vaccines affect fertility?

COVID-19 vaccination is recommended for people who are pregnant, breastfeeding, trying to get pregnant now, or might become pregnant in the future. Pregnant and recently pregnant people are more likely to get severely ill with COVID-19 compared with non-pregnant people. Breastfeeding is rarely a safety concern with vaccines. There is no evidence that COVID-19 vaccines can reduce fertility.

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Why was use of the J&J/Janssen one-dose vaccine temporarily paused?

The Centers for Disease Control and Prevention (CDC) and US Food and Drug Administration (FDA) temporarily recommended a pause in the use of the J&J/Janssen COVID-19 vaccine to allow experts time to better understand the small number of reported cases of women developing a rare clotting disorder after receiving the vaccine. All reported cases were in women age 18-48 years, and symptoms occurred 6-13 days after vaccination. More than 7.5 million doses of the vaccine had been administered in the US at the time of the pause.

The pause was lifted on April 23, 2021, after scientists reviewed the data and concluded that the benefits of the vaccine far outweigh the risks. Women younger than 50 years old should be aware of the rare risk of blood clots with low platelets after vaccination, and that other COVID-19 vaccines are available where this risk has not been seen. 

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How long after receiving a COVID-19 vaccine can I take an antibiotic safely?

There is no influence or interaction between antibiotics and COVID-19 vaccines, so when indicated, antibiotics may be taken at any time relative to COVID-19 vaccine administration.

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Is it possible to get COVID-19 after receiving the vaccine?

None of the new vaccines contain the live virus that causes COVID-19, so it is not possible to get the disease from the vaccine.

It typically takes a few weeks for the body to build immunity after vaccination. That means it is possible for an individual to be infected with the virus that causes COVID-19 just before or just after vaccination, as the vaccine has not had enough time to provide protection.

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Getting Vaccinated

After I have been fully vaccinated, do I still need to wear a mask and take other precautions?

If you are fully vaccinated, you can do many things that you did before the pandemic. Even if you are fully vaccinated, the Centers for Disease Control and Prevention (CDC) still recommends wearing a mask in certain instances, and you still need to follow guidance at local businesses and workplaces.

Anyone who is not fully vaccinated still needs to wear a face mask, practice social distancing, and take other precautions. Face masks can help prevent an infected individual from spreading the virus. Face masks are not recommended for children less than two years of age or for individuals who have trouble breathing or who cannot easily remove them.

Wearing a mask is most important if you have a weakened immune system or if, because of your age or an underlying medical condition, you are at increased risk for severe disease, or if someone in your household has a weakened immune system, is at increased risk for severe disease, or is unvaccinated. If this applies to you or your household, you might choose to wear a mask regardless of the level of transmission in your area.

In the US, people are still getting sick, being hospitalized, and dying due to COVID-19. Precautions such as wearing masks in public places, staying at least 6 feet apart from others, and avoiding crowds and poorly ventilated spaces can help stop the spread of COVID-19.

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If I already had COVID-19, do I still need to get vaccinated?

CDC recommends COVID-19 vaccination regardless of whether or not an individual was previously infected.

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Should I delay my COVID-19 vaccine if I am scheduled for surgery?

There is no need to delay getting vaccinated against COVID-19 until after surgery. Fever is a potential side effect of COVID-19 vaccines, and having a fever after surgery raises concerns about a possible surgical wound infection. For that reason, it is a good idea to allow at least one week between getting vaccinated and having surgery.

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What side effects should people expect from the vaccines?

Some individuals who are vaccinated may have a sore arm, fever, or other symptoms. These symptoms are normal and are a sign that the body is building immunity.

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What can be done to relieve side effects of COVID-19 vaccines?

Side effects are normal signs that the body is building immunity. These side effects usually go away in a few days. Over-the-counter medicines, such as aspirin, antihistamines, or acetaminophen, may help relieve fever, pain, or discomfort after getting vaccinated—but should not be used before getting vaccinated.

To reduce pain and discomfort in the arm, apply a clean, cool, wet washcloth over the area, and use/exercise your arm gently. To reduce discomfort from fever, drink plenty of fluids and dress in layers that can be removed.

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What is the purpose of my COVID-19 vaccination card, and what should I do if I lose it?

The COVID-19 vaccination card is simply a medical record to help keep track of which type of vaccine you received, when you received it, and when you are due for another dose if necessary. You should keep your vaccination record in a safe place, as with all medical records. It is a good idea to make a copy of the vaccination card and keep the copy secure as well. Avoid carrying the card in your wallet to prevent losing it. Laminating the card is not necessary, and can make it difficult to add booster doses if needed. If you lose your card, contact the site where you received your vaccine or your local health department for a replacement.

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Will I be required to show proof of vaccination to return to work or school?

Vaccine mandates cannot be imposed federally, but some employers or schools may require proof of vaccination.

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What steps should those who have been fully vaccinated take if they are exposed to someone with COVID-19?

Fully vaccinated individuals who have had close contact with someone who has COVID-19 should get tested and should isolate for 10 days if the test result is positive.

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Who should not receive COVID-19 vaccines?

Authorized COVID-19 vaccines are safe for most people:

  • Current vaccines are not authorized for children less than 12 years of age
  • Individuals who have had severe allergic reactions to other vaccines or injectable therapies should not get vaccinated against COVID-19. Those with other allergies may be vaccinated but should remain at the vaccination site for 15-30 minutes for observation, following vaccination.
  • There are no known safety issues for pregnant or breastfeeding women
  • COVID-19 vaccination is recommended for those who have previously tested positive for COVID-19

Women younger than age 50 years should be aware of the rare risk of blood clots with low platelets after vaccination with the J&J/Janssen COVID-19 vaccine. Other COVID-19 vaccines are available where this risk has not been seen.

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When can we expect to return to normal?

Recommended public health measures (including social distancing, face masks, and handwashing) will still be necessary to help stop the spread of COVID-19:

  • While the vaccines appear to be highly effective at preventing disease, they may not prevent asymptomatic infection, meaning that those who have been vaccinated might still be able to get infected without experiencing any symptoms, and, therefore, unknowingly spread the virus.
  • Scientists estimate that to control COVID-19, about 70-80 percent will need to be immune (~250 million individuals in the US). To rely on infections alone to stop the spread of COVID-19, between 1 million and 5.4 million people would die before 250 million become immune.
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Interaction with Antibiotics and Other Drugs

Do COVID-19 vaccines interfere with other drugs and medications?

COVID-19 vaccines do not interfere with the vast majority of prescription and over-the-counter drugs that can be taken safely and effectively by those receiving COVID-19 vaccines. Talk to a healthcare professional if you have specific questions about your medical care.

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Is it safe to take an antibiotic before or after receiving a COVID-19 vaccine?

COVID-19 vaccines do not influence or interact with antibiotics, so when indicated, antibiotics may be taken at any time relative to COVID-19 vaccine administration.

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Is it safe to take a pain reliever when getting a COVID-19 vaccine?

Do not take a pain reliever or fever-reducing drug before receiving a COVID-19 vaccine because these drugs may impact the immune response to the vaccine. If you experience side effects after getting vaccinated, it is safe to take these drugs as needed to treat pain. Patients routinely taking low-dose aspirin or anti-inflammatory medications may continue to take these medications as instructed.

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Is it safe to get a COVID-19 vaccine while taking medication to control a chronic health condition?

COVID-19 vaccines do not interfere with drugs that are taken to control blood pressure, diabetes, cholesterol, lung disease, or other chronic health conditions. COVID-19 vaccines only affect the immune system, which has no impact on the effectiveness of medications to manage chronic conditions.

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Do any drugs or medicines impact the effectiveness of COVID-19 vaccines?

Prescription drugs that affect the immune system—such as certain cancer chemotherapies or drugs for HIV or autoimmune diseases—may impact the effectiveness of COVID-19 vaccines. Even if they do not prevent disease entirely, COVID-19 vaccines can help prevent hospitalization or death, and prescription drugs used to treat other conditions will continue to work when taken as directed.

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Updated August 2021

Sources: Centers for Disease Control and Prevention, Food and Drug Administration

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