COVID-19 Vaccine Frequently Asked Questions

Get answers to common and evolving questions around a COVID-19 vaccine.

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You may. A vaccine booster is recommended to anyone 12+ who received the Pfizer-BioNTech, Moderna or Janssen/Johnson & Johnson vaccine.

People with moderately to severely compromised immune systems are especially vulnerable to COVID-19 and may not build the same level of immunity to a two-dose vaccine series compared to people who are not immunocompromised. For these individuals, CDC recommends an additional dose of mRNA COVID-19 vaccine at least 28 days after a second dose of the Pfizer-BioNTech or Moderna COVID-19 vaccine for these individuals. People with moderately to severely compromised immune systems can also receive a booster dose 5 months after their additional dose of COVID-19 vaccine.

Speak with your healthcare provider about getting a COVID-19 booster vaccine.

For more information on booster doses visit the Centers for Disease Control and Prevention website.

There is no exact date. The reason COVID-19 vaccines are safe and effective is because there is a rigorous process all vaccines go through before they become widely available. You can learn more about how vaccines are approved at

SARS-CoV-2, the virus that causes COVID-19, is a type of coronavirus. Like all viruses, coronaviruses change constantly through mutation, resulting in new variants such as Omicron. The CDC closely monitors variants and has posted information about Omicron. The ways to protect yourself from coronavirus infection haven’t changed. You should be up to date on your recommended COVID-19 vaccinations, including boosters. Boosters are available for everyone 12+. Continue washing your hands and stay home when you are sick. Masking provides an additional layer of protection and CDC recommends wearing a mask in public indoor settings where community transmission is substantial or high. Until you are fully vaccinated, maintain social distance from others and wear a mask around those who do not live in your household. Remember that breakthrough infections are expected in fully vaccinated people. Vaccines are effective at preventing severe illness, hospitalization, and death.

It can be confusing, and there are a lot of terms floating around. Here’s a brief summary of each:

  • Unvaccinated: I haven’t received a COVID-19 vaccine.
  • Partially vaccinated: I received only the first of two doses of the Pfizer or Moderna vaccine.
  • Fully vaccinated: I completed a series of Pfizer or Moderna vaccine or received the one-dose Johnson & Johnson/Janssen vaccine. If I am immunocompromised, I also received a third dose.
  • Boosted: After being fully vaccinated, I received an additional dose.
  • Up to date: I have received all eligible COVID-19 vaccinations.

You can learn more about the types of vaccines available, where to find a vaccine, how to talk to others about getting vaccinated by visiting

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What You Need to Know about Kids and COVID-19 Vaccines

Get information on vaccine availability for children and read frequently asked questions about kids and the COVID-19 vaccine. 

Before Getting Vaccinated

State health departments are providing information on when and where vaccines are available. Find your state health department using our lookup tool. You can also search for availability through your local pharmacy by visiting

No. Like the flu shot and other vaccines, COVID-19 vaccines cannot give you the virus.

Yes. So far, studies suggest that the currently available vaccines work on variants circulating across the U.S. and globe. Many of the more common variants allow the virus to spread more easily, making it especially important to get vaccinated as soon as possible. If you are not yet up to date on your COVID-19 vaccinations including boosters, protect yourself by following recommendations for wearing a face mask and maintaining social distance. And maintain good health practices such as washing your hands and avoiding unnecessary exposure to people who are sick.

You can view reports from the CDC showing which variants are currently most common in the United States.

Yes. Due to the severe health risks associated with COVID-19 and the fact that reinfection with COVID-19 is possible, you should be vaccinated regardless of whether you already had COVID-19 infection. If you were treated for COVID-19 symptoms 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.

If you are currently sick with COVID-19, you should wait until you are recovered from your illness and discontinued quarantine before getting a COVID-19 vaccination.

Yes. It is important for everyone to get vaccinated as soon as they are eligible because this will help reduce the transmission of COVID-19 overall, as well as provide protective immunity for the individual who is vaccinated. The American Lung Association encourages you to speak with your child’s healthcare provider about any concerns you have.

Currently there is one vaccine, made my Pfizer-BioNTech, that is available for use by everyone 5 years and older.

Get more information about vaccines and COVID-19 in children.

Having seasonal or food allergies does not mean you will experience a reaction to the vaccine. If you have a history of severe allergic reactions, you should talk to your physician before receiving an mRNA COVID-19 vaccination. They will help you determine if you have experienced a severe allergic reaction (e.g., anaphylaxis) to any component of a COVID-19 vaccine listed in the prescribing information, in which case the vaccine would not be recommended. Established COVID-19 vaccination protocols suggest all persons be observed after vaccination for a minimum of 15 minutes.

Yes. Whether you are trying to get pregnant now, or want to get pregnant in the future, you may get a COVID-19 vaccine that protects you against severe illness from COVID-19. Misinformation is circulating and that can be confusing. There isn’t any evidence that any of the COVID-19 vaccines currently available cause problems with pregnancy or the development of the placenta. There has never been any evidence of fertility problems as a side effect for any vaccine, including COVID-19 vaccines. Speak with your healthcare provider if you have concerns so they can help you address them with science-based information.

There have been cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the outer lining of the heart) following mRNA COVID-19 vaccination. These cases typically occur in male adolescents and young adults after the second dose, and within a week of vaccination. It is important to seek medical care if symptomatic (chest pain, shortness of breath, having a fast beating, fluttering, or pounding heart). Most patients respond well to treatment and quickly feel better.

It is still recommended that everyone ages 5 years and older get vaccinated for COVID-19. The known risks of COVID-19 illness exceed the potential risks of a rare adverse reaction to vaccination, including the possible risk of myocarditis or pericarditis.

No, vaccines were granted emergency use authorization because they were deemed safe and effective. The U.S. Food and Drug Administration’s (FDA’s) Center for Biologics Evaluation and Research is responsible for regulating vaccines in the United States. And each vaccine producer must follow a multi-step approval process that includes sharing research from clinical trials.

FDA can also require a manufacturer to submit the results of their own tests for potency, safety, and purity for each vaccine lot. Vaccines typically require years of research and testing before reaching the public, but scientists banded together across the globe to produce a safe and effective coronavirus vaccine more quickly.  This doesn’t mean that the vaccine is less safe, it just means that the whole world is keen to ensure that we are protected from this new threat to lung health and so researchers have been working collaboratively to build a knowledge base of what works and achieved success quickly.

The CDC has more information about COVID-19 vaccine safety.

After approving a vaccine, FDA continues to oversee its production to ensure continuing safety. Monitoring of the vaccine and of production activities, including periodic facility inspections, must continue as long as the manufacturer holds a license for the vaccine product. 

V-safe is a smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins after you receive a COVID-19 vaccination. Through v-safe, you can quickly tell CDC if you have any side effects after getting the COVID-19 vaccine. Depending on your answers, someone from CDC may call to check on you. And v-safe will remind you to get your second COVID-19 vaccine dose if you need one. 

In addition, the Vaccine Adverse Event Reporting System (VAERS) is a national vaccine safety surveillance program that collects and analyzes side effects that occur. Reports from patients, providers, pharmacists and vaccine manufacturers can all be submitted to VAERS.   

The CDC has more information about COVID-19 vaccine safety.

Choosing a Vaccine

here are three types of vaccines that work in different ways:

  • Messenger RNA (mRNA) vaccines contain a copy of genetic information that looks like the SARS-CoV2 (the virus that causes COVID-19) virus’s information that causes COVID-19.  This gives our cells instructions for how to make a harmless protein that is unique to the virus. After our cells make copies of the protein, our bodies recognize that the protein should not be there and build T-lymphocytes and B-lymphocytes and antibodies that will remember how to fight the virus that causes COVID-19 if we encounter the virus in the future. The Moderna and Pfizer vaccines are mRNA vaccines are currently preferred by the CDC in the United States.
  • Viral vector vaccines contain a modified, weakened virus (not the COVID-19 virus) that delivers a message for a protein like the spike protein of the SARS-CoV2 virus to be made by our cells.  By instructing cells to make large amounts of antigen, which then triggers an immune response, the vaccine mimics what happens during natural infection with SARS-CoV2 and stimulates an immune response that will protect you from future encounters from the COVID-19 virus. The AstraZeneca and Johnson & Johnson vaccines are examples of these. The AstraZeneca vaccine is not available in the United States. The Johnson & Johnson/Janssen vaccine is no longer a CDC preferred vaccine however, it is available in for individuals in certain cases.
  • Protein-based vaccines contain harmless coronavirus proteins, not the whole virus, and produces an immune response against the virus. The Novavax vaccine is an example of protein-based vaccines. Currently there are no protein-based vaccines available in the United States.

A preferential recommendation is given when one or more vaccine products are recommended before the use of other available vaccine products. This is usually due to vaccine safety concerns, vaccine effectiveness or a combination of both.

A second dose of mRNA COVID-19 vaccine should not be received earlier than the recommended schedule.

The second dose of COVID-19 vaccine should be administered as close to the recommended interval as possible. If you don’t receive your second shot of COVID-19 vaccine up to 4 days before or after the recommended date, you do not have to restart the vaccine series.

Yes, for boosters only. The CDC allows individuals to choose which vaccine they receive as a booster The Pfizer-BioNTech and Moderna vaccines are preferred. You can still get a Johnson & Johnson/Janssen vaccine though it is not a preferred COVID-19 vaccine.

Johnson & Johnson/Janssen Vaccine

Over 490 million COVID-19 vaccines have been given in the United States since they became available a year ago. This allows for CDC to gather a lot of data on the safety and efficacy of the available vaccines. Based on the availability of safety and vaccine effectiveness data, the ACIP and CDC determined that the mRNA (Pfizer-BioNTech and Moderna) vaccines have better risk/benefit balance meaning they work better and have less safety issues than the Johnson & Johnson vaccine.

The incidence of two rare adverse events thrombosis with thrombocytopenia (TTS), Guillain-Barré syndrome (GBS) and lower vaccine effectiveness with the Johnson & Johnson vaccine are what resulted in the preferential recommendation for mRNA vaccines.

Guillain-Barré Syndrome (GBS) is a rare condition where a person’s immune system damages the nerves, causing weakness and sometimes paralysis. GBS usually resolves fully on its own but can last for several weeks to several years. Symptoms of GBS include:

  • Weakness and tingling in the legs that may progress to the arms and upper body
  • Symptoms may continue to increase until some muscles cannot be used
  • In severe cases, paralysis

Thrombosis with thrombocytopenia syndrome (TTS) is a rare but potentially fatal condition.

Thrombosis happens when blood clots block blood vessels. Symptoms of thrombosis include:

  • Pain and swelling in an extremity (hand, food, arm, leg, etc.)
  • Chest pain
  • Numbness/weakness in one side of the body
  • Sudden change in mental status

Thrombosis can potentially cause a heart attack or stroke.

Thrombocytopenia is a condition where you have low blood platelets. Platelets are blood cells that help your blood clot and stop bleeding when you’re injured.

Thrombocytopenia can potentially cause internal bleeding and bleeding into the brain.

Yes. If you choose to receive the Johnson & Johnson vaccine, you will still have access to it. Receiving any vaccine provides better protection than the risk of becoming seriously ill with COVID-19 if you are unvaccinated. More information about the Johnson & Johnson vaccine can be found on the CDC site.

Yes. The CDC has confirmed that you remain fully vaccinated if you received the Johnson & Johnson/Janssen vaccine at least two weeks ago. Additionally, you do not need to start over with the Pfizer-BioNTech or Moderna vaccines. If you have not received a booster, it is now recommended that you consider a Pfizer-BioNTech or Moderna vaccine as a booster.

After Getting Vaccinated

Once you're fully vaccinated (2 weeks after second dose of Pfizer or Moderna vaccines, or 2 weeks after a single-dose Johnson & Johnson vaccine) you can start doing some activities you had to stop because of the pandemic. The CDC has more guidance on how to be safe once you're fully vaccinated.

Yes, it is possible. What you are referring to is also called breakthrough infection, when fully vaccinated individuals become ill with COVID-19. These individuals tend to have less severe illness than unvaccinated people. No vaccine is 100% effective and emerging variants can decrease vaccine effectiveness. Because of the emergence of variants, CDC recommends booster shots for those eligible. The currently available vaccines are expected to protect against severe illness, hospitalizations and death with the currently circulating Omicron variant. Vaccines provide immunity against SARS-CoV-2, which we had no immunity whatsoever from pre-pandemic, they are a huge advantage to protecting your health.

New guidance from the CDC recommends mask wearing in public indoor settings if you are in an area with substantial or high transmission. You can check community transmission using CDC's Data Tracker. Other reasons to consider wearing a mask when inside public indoor settings include if you are immunocompromised, at increased risk for severe disease or have someone in your home who is one of those or not fully vaccinated. Vaccination remains the best protection against severe illness from COVID-19, caused by the highly transmittable Omicron variant warranting further protection against the sustained community spread occurring in much of the country.

Not everyone experiences side effects from the COVID-19 vaccine, but some common side effects include pain, swelling and redness at the injection site. You may also experience any of the following: tiredness, headache, muscle pain, chills, fever or nausea. These side effects might affect your ability to do daily activities but should go away in a few days. Serious side effects causing long-term health problems are extremely unlikely following any vaccination, including COVID-19 vaccination.

A key reason to get vaccinated is to protect against having severe complications up to and including death, especially among those who are in the high-risk group. So, although it is important to be aware of safety and side effect issues around the vaccine, each person should weigh these usually mild side effects of arm soreness and fatigue for a day or two against the great benefit of protecting against moderate to severe illness which can occur at any age and in people without any underlying conditions.

If you have pain or discomfort following your COVID-19 vaccine, speak with your healthcare provider about taking an over-the-counter medication like ibuprofen or acetaminophen. It is important to take pain reliever after the vaccination, not before.

If you are experiencing pain where you got your shot you could try applying a clean, cool, wet washcloth to the injection area and be sure to use or exercise your arm. If you are experiencing discomfort from a fever, you can drink plenty of fluids and dress lightly.

Remember that side effects may be more intense after your second shot and are normal signs that your body is building protection and should go away within a few days.  You should contact your healthcare provider if the redness or tenderness where you got your shot gets worse after 24 hours or if your side effects are worrying you and not gone after a few days.  

Millions of people in the United States have received COVID-19 vaccines and they are safe and effective at protecting against COVID-19. Some people experience no side effects after vaccination while many will experience mild side effects, such as pain, swelling at the injection site, a headache, chills or a fever. A small number of individuals will experience a severe allergic reaction to an ingredient in the vaccine, but that is extremely rare and the reason for observation immediately after being vaccinated. Discuss with your healthcare provider any side effects that concern you.

You can help monitor for side effects using V-safe, a smartphone-based health checker if you have received a COVID-19 vaccine in the past six weeks. Using text messages and web surveys, it allows individuals who track any side effects and will follow up via phone with anyone who reports a medically significant adverse event.

Have a question not addressed in our FAQ? Contact our Lung HelpLine at 1-800-LUNGUSA for one-on-one support, or submit your question online.

The American Lung Association urges members of the public to always consult with their own healthcare providers about whether this or any vaccine is appropriate for them.

Page last updated: January 21, 2022

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