About the current FDA-emergency use authorized COVID-19 vaccines

  • Why did the FDA suspend the Johnson & Johnson (Janssen) vaccine?

    The Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) announced a potential safety concern about the Johnson & Johnson (Janssen) COVID-19 vaccine. The FDA and CDC have asked to pause use of the Johnson & Johnson vaccine out of an abundance of caution so they can complete an investigation. Mass General Brigham has stopped administration of this vaccine while the CDC and FDA continue to investigate.

    There have been very rare reports of a type of blood clot called cerebral venous sinus thrombosis among patients that have received the Johnson & Johnson vaccine. Out of nearly 7 million Johnson & Johnson vaccine administrations in the U.S., there have been 6 reported cases of blood clots. The reports have all occurred between 6 and 13 days after receiving the vaccine, occurring in women between 18 and 48 with low platelets.

  • What should I do if I received the Johnson & Johnson vaccine?

    If you have received the Johnson & Johnson vaccine within the past month, please call your health care team immediately if you have symptoms of:

    • Headache that is constant, may be worse with changes in position (bending over), and/or associated with nausea, vomiting, or vision changes
    • Headache that resolved within 24 hours of getting the vaccine and then came back
    • Abdominal pain, leg swelling, chest pain, shortness of breath, or bruising

    You do not have to call your doctor if you had symptoms of headache, muscle aches, or other side effects within 24 hours of receiving the Johnson & Johnson vaccine and the symptoms have now gone away. If you received the Johnson & Johnson vaccine over a month ago, we do not believe you to be at risk for this potential side effect.

  • How does the Johnson & Johnson vaccine work?

    The Johnson & Johnson vaccine is not an mRNA vaccine. It is an adenovirus vector vaccine. It uses a modified version of the common cold virus called adenovirus 26 to deliver directions to your body to make the spike protein found on the surface of the coronavirus. Your immune system can then make antibodies to these proteins to protect you against COVID-19. You cannot get the cold from the vaccine.

  • Are the vaccines safe?

    We will not recommend any vaccine that we do not feel is safe and effective. The COVID-19 vaccines have been tested using large-scale clinical trials with many thousands of people from different races, ages, and backgrounds. Every vaccine goes through a strict regulatory review process. We continually monitor any clinical or safety concerns for all vaccines.

    As of April 13, the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) announced a potential safety concern about the Johnson & Johnson COVID-19 vaccine. The FDA and CDC have asked to pause use of the Johnson & Johnson vaccine out of an abundance of caution so they can complete an investigation. Mass General Brigham has stopped administration of this vaccine while the CDC and FDA continue to investigate.

  • The Pfizer and Moderna COVID-19 vaccines are mRNA vaccines. What does that mean?

    Though mRNA vaccines are a new kind of vaccine, researchers have been studying and working on them for many years. They do not contain live virus and cannot cause COVID-19. Instead, they give our cells directions on how to make the COVID-19 proteins found on the outside layer of the coronavirus. Our immune system can then make antibodies to these proteins and protect us from being infected with COVID-19. The mRNA from the vaccine never enters the nucleus of our cells or gets into our DNA. The CDC has information about mRNA vaccines.

  • Can I get COVID-19 from a vaccine?

    No. The vaccines (Pfizer, Moderna, or Johnson & Johnson) do not contain the whole or live virus and therefore cannot cause COVID-19.

  • How do we know the vaccines work? Is the Johnson & Johnson vaccine as effective at protecting against COVID-19 as the other vaccine options?

    All COVID-19 vaccines have proven to be extremely effective. According to Phase 3 trials, the Pfizer vaccine is 95% effective 7 days after the second dose. The Moderna vaccine is 94% effective 14 days after the second dose. These results were consistent across gender, age, race, and ethnicity.

    According to clinical trials, the Janssen (Johnson & Johnson) vaccine is 85% effective against severe COVID-19 disease. It also provides 100% protection against hospitalization and death from COVID-19. 

  • How long will immunity last after I get vaccinated? Will I need to be vaccinated every year?

    We do not know this yet. The clinical trials will continue to monitor participants to see how long protection lasts. We will provide updated information as it becomes available.

    Because we don’t yet know how long immunity will last, it’s still important to wash your hands, wear a mask, and socially distance.

  • I already had COVID-19. Should I get vaccinated?

    Yes, you can still get vaccinated if you have had COVID-19 and have recovered.

    However, you should not get vaccinated if:

  • Can I get a COVID-19 vaccine with other vaccines?

    When possible, you should not get other vaccines for 14 days before or after you get the COVID-19 vaccine. If you get a COVID-19 vaccine within 14 days of another vaccine, you do not have to get it again.

  • What are the side effects of a COVID-19 vaccine?

    Some people do get side effects after receiving the vaccine. For most people, mild side effects resolve within a day or so.

    • The most commonly reported symptoms from the Pfizer vaccine are pain at the site of vaccination, fatigue, headache, muscle pain, joint pain, and chills. 
    • The most commonly reported symptoms from the Moderna vaccine are pain at the injection site, tiredness, headache, muscle pain, chills, joint pain, swollen lymph nodes in the same arm as the injection, nausea and vomiting, and fever.
    • The most commonly reported symptoms from the Johnson & Johnson vaccine are pain at the injection site, headache, fatigue, muscle aches and nausea. 

    Read more about potential side effects

  • Will you choose which vaccine to give to patients based on their age, conditions, or other risk factors?

    Mass General Brigham cannot personalize which vaccine (Pfizer, Moderna) individual patients receive. Our vaccine supply is provided by the state and federal government, and we do not choose which vaccines we get in our distribution.

  • I have a preference for a specific vaccine. Can I wait until you have more of that vaccine?

    People receiving vaccination will not have the option to select which vaccine they receive. Please note that we have paused administration of the Johnson & Johnson vaccine while the CDC and FDA investigate reports of rare blood clots.

    The best vaccine is the one that is available to you on the day of your appointment. All vaccine options available to our patients are safe and highly effective.

    At this time, we are primarily giving the Pfizer vaccine at our clinics.

    The Pfizer and Moderna vaccines both require two doses. After you receive your first dose, your second dose will be from the same manufacturer. That means if your first dose is the Pfizer vaccine, your second dose will also be Pfizer; if your first dose is the Moderna vaccine, your second dose will also be Moderna.

Masks and social distancing

  • Can I stop wearing masks and social distancing after getting vaccinated?

    Not in public spaces. We know that the vaccines protect you from getting sick, but we do not know if they stop you from giving it to other people. Because not everyone will get vaccinated right away, we must be careful to protect others. Even if you get vaccinated, you should still wear a mask, practice social distancing, and wash your hands. Infection control experts will let us know when it is safe to change or stop these safety measures.

  • When am I fully vaccinated? 

    You are considered fully vaccinated if it has been:

    • 2 weeks since getting the single-dose Johnson & Johnson vaccine or 
    • 2 weeks since getting the second dose of the Pfizer or Moderna vaccine

    If it’s been less than 2 weeks, you are not fully vaccinated. 

  • Can I stop wearing masks and social distancing with people who are fully vaccinated?

    If you are fully vaccinated, you can gather indoors, privately, with other fully vaccinated people without wearing a mask. You can gather indoors with unvaccinated people from one other household without masks if everyone in the unvaccinated household is low risk for COVID-19 complications. Please note that this does not apply to health care settings or public settings. Other workplaces may have other guidelines. 

    Patients with solid organ transplants should speak with their transplant care team to discuss recommendations about masking and social distancing.

    You should still wear masks and social distance in public and when gathering with unvaccinated people from more than one household. If you have symptoms, you should talk to your health care provider. You may need to be tested for COVID-19. See more information on the CDC website

  • Why do we need to get a COVID-19 vaccine if we’re wearing masks and social distancing?

    We need to use all the tools available to us to stop the pandemic. Together, the COVID-19 vaccines and simple everyday actions, like wearing a mask and social distancing, will offer the best protection from COVID-19. And even though the vaccines are very effective, we still don’t know how effective vaccination will be for you. A small number of people who are vaccinated may still get the virus. You should do everything you can to prevent getting the virus and passing it to others.


  • Does the COVID-19 vaccines cause allergic reactions?

    There have been some reports of people having allergic reactions after getting vaccinated. A small number of people had a severe allergic reaction called anaphylaxis. Based on this, the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention (CDC) recommend that people with a history of anaphylaxis to any of the ingredients in a COVID-19 vaccine should not get that vaccine. People with other food or medication allergies can be vaccinated.

    In general, most patients allergic to one vaccine can receive the other vaccines safely. If you have a history of severe allergic reactions to vaccines, injectable therapies, or any component of the COVID-19 vaccine you are going to receive, you should talk to your primary care provider or allergist (if you have one). Your provider can help you decide if it is safe to get vaccinated.  

    Read more about potential side effects

  • Can I get the COVID-19 vaccines if I have a food or drug allergy?

    You can receive a COVID-19 vaccine if you have a food or drug allergy. The Pfizer, Moderna, and Johnson & Johnson COVID-19 vaccines do not contain gelatin, egg, or latex. Nevertheless, if you have a history of anaphylaxis due to any cause (food, oral medications, venom, latex), you might be observed for 30 minutes after receiving the vaccine.

  • What are the ingredients in the COVID-19 vaccines?

    The Pfizer,  Moderna, and Johnson & Johnson COVID-19 vaccines do not contain gelatin, egg, or latex. Also, the vial stoppers are not made with natural rubber latex. Patients who have latex allergies can receive the Pfizer, Moderna, and Johnson & Johnson COVID-19 vaccines. 

    Both the Pfizer and Moderna COVID-19 vaccines contain polyethylene glycol. Reactions to polyethylene glycol are very rare. Patients with a history of having an allergic reaction to polyethylene glycol should talk to their provider before receiving either the Pfizer or Moderna vaccine. 

    Ingredients of the COVID-19 vaccines

    Scroll to the right to view the full table below.

      Pfzier-BioNTech Moderna Janssen (Johnson & Johnson)
    Active Nucleoside-modified messenger RNA (modRNA) encoding the viral spike (S) glycoprotein of SARS-CoV-2. Nucleoside-modified mRNA encoding the viral spike (S) glycoprotein of SARS-CoV-2 Recombinant, replication-incompetent adenovirus type 26 expressing the SARS-CoV-2 spike protein
    Inactive - lipids
    • (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate)
    • 2[(polyethylene glycol [PEG])-2000]-N,N-ditetradecylacetamide
    • 1,2-distearoyl-sn-glycero-3-phosphocholine
    • Cholesterol
    • SM-102 (Proprietary to Moderna) 
    • Polyethylene glycol (PEG) 2000 dimyristoyl glycerol (DMG)
    • 1,2-distearoyl-sn-glycero-3-phosphocholine
    • Cholesterol 
    • 2-hydroxypropyl-β-cyclodextrin (HBCD)
    • Polysorbate-80
    Inactive – salts, sugars, buffers 
    • Potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate
    • Sugar (sucrose)
    • The diluent, added to the vaccine for administration, is saline (sodium chloride)
    • Tromethamine, tromethamine hydrochloride, acetic acid, sodium acetate
    • Sugar (sucrose)
    • No diluent needed
    • Citric acid monohydrate, trisodium citrate dihydrate
    • Ethanol
    • Sodium chloride
  • What is a vaccine allergy?

    Similar to medication or food allergies, people can be allergic to an ingredient in a vaccine. About half of allergic reactions to vaccines happen in the first 15 minutes after receiving vaccination, and 90% occur within the first 30 minutes. Most vaccine allergic reactions are mild, such as hives. A severe allergic reaction is called anaphylaxis, which are very rare, occurring in one in a million people for most vaccines. Symptoms of anaphylaxis almost always occur within 4 hours of vaccination, most often within minutes. Symptoms usually include multiple parts of the body: hives on the skin; swelling of mouth, lips, tongue or throat; shortness of breath, wheezing, or chest tightness; or low blood pressure or loss of consciousness.

  • What happens if I have a reaction to the COVID-19 vaccine?

    Because most allergic reactions happen within the first 15–30 minutes, all patients are observed for 15 minutes after getting vaccinated to watch for an allergic reaction. If you have a history of anaphylaxis, you may have a 30-minute observation period after getting vaccinated. If you do have an allergic reaction, medical staff will treat you immediately. All vaccine locations can diagnose and manage allergic reactions and have medications, including epinephrine (“Epi-Pen”), available.

Immunocompromised patients

  • I am immunocompromised. Should I get a COVID-19 vaccine?

    The CDC says that people who are immunocompromised may be vaccinated against COVID-19, as long as they have had no issues with getting vaccines in the past. For questions about allergies related to COVID-19 vaccination, please see the allergy frequently asked questions.

    Please note, the COVID-19 vaccines are not live vaccines; live vaccines are often not recommended for immunocompromised patients. 

    Patients who are immunocompromised include people:  

    • Living with HIV
    • On immunosuppressive therapies like steroids (prednisone) for a long time
    • On immunosuppressive therapies for prevention of organ transplant rejection
    • On immune altering medications like biologic therapies (often injectable). These are used for treatment of autoimmune diseases such as Crohn’s disease, rheumatoid arthritis, lupus, and others.

    We do not yet know how effective the COVID-19 vaccines will be for you. You may have less of an immune response when you get vaccinated. Even if you get vaccinated, you should still wear a mask, practice social distancing, and wash your hands. Please see the frequently asked questions about masks and social distancing. This is true for everyone getting vaccinated now. Infection control experts will let us know when it is safe to change or stop these safety measures.

    For now, we do not know if you may need long-term boosters or revaccination. Mass General Brigham may not start repeat vaccination until everyone is vaccinated.

  • Should I change my immunosuppression medications when I get the vaccine?

    In general, we do not recommend altering the immunosuppression before or after vaccination. In specific cases, your provider may recommend changes. If you have questions, discuss this during your next medical visit.

  • Can I get a COVID-19 vaccine if I have had an organ transplant?

    You can get vaccinated. It’s possible that a COVID-19 vaccination may be less effective for you. It may be best to wait to get vaccinated at least 3 months after your transplant, if possible, to improve the immune response to the vaccine you receive (when you are on less immune suppression). There is no preference for the Pfizer-BioNTech or Moderna vaccines. Your transplant provider will tell you if you need transplant labs after vaccination.

  • If I’ve had a solid organ transplant, can I stop wearing a mask if I’ve been vaccinated?

    Solid organ transplant patients should remain vigilant in following COVID-19 precautions even if you have been vaccinated. We are still learning more about the level of protection after vaccination in organ transplant patients. 

    While the CDC has updated its guidelines for fully vaccinated people, we ask that you continue to refrain from gathering with individuals who are not in your household, regardless of vaccination status. We recommend that you:

    • Not gather with family/friends who do not live in your household, unmasked and less than 6 feet apart, despite their vaccination status. Vaccinated individuals might be able to spread the virus to others.
    • Wear a well-fitting mask when outside your home. 
    • Wash your hands frequently, especially before eating. 
    • Stay at least 6 feet (2 arms lengths) apart from others that don't live with you.
    • Avoid crowds and poorly ventilated spaces. The more people you are in contact with, the more likely you are to be exposed to COVID-19.
    • Do not travel at this time.

    Per CDC guidelines, we are not recommending antibody testing at this time. We are still testing the best methods to determine immunity. We do not know what level of antibodies would provide protection in transplant patients. We hope to have more information soon. 

  • I am waiting for organ transplantation. Should I get vaccinated?

    In general, vaccines work better before organ transplant, before the immunosuppression has started. If possible, we would recommend that you get vaccinated before transplant.

Pregnancy and breastfeeding

  • I am pregnant. Should I get a COVID-19 vaccine?

    You should discuss the best option for you with your OB/GYN. This will be based on your risk for exposure to the virus and how sick you might get if you do get the virus.

    Vaccination, especially with vaccines that do not contain live virus, is considered a safe and routine part of prenatal care. For example, the flu shot is encouraged during pregnancy. In line with recommendations from the CDC, COVID-19 vaccination is offered to pregnant people.

  • Is the vaccine safe for pregnant people?

    The CDC, the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine all agree that the Pfizer and Moderna COVID-19 vaccines should be offered to all pregnant and breastfeeding individuals who are eligible for vaccination.

    You should speak with your OB/GYN about whether or not you should get vaccinated. Both the virus and the COVID-19 vaccines are new. There is very little data on the safety of these vaccines in pregnancy. Pregnant people were not included in the clinical trials for the vaccines. However, like many new medications and vaccines, the COVID-19 vaccines were studied in pregnant animals. These studies did not show any complications related to fetal development after vaccination. 

  • I’m pregnant. Does it matter when I get vaccinated?

    The decision about when you get vaccinated should be made together with your OB/GYN. This should consider your risk of exposure to the virus and what your chance of getting very sick might be if you do get the virus. There is no data to suggest that the COVID-19 vaccines cause miscarriage.

  • I heard that some people had reactions after vaccination. Are these dangerous in pregnancy?

    Symptoms including fever, muscle aches, joint pains, fatigue, and headache are common side effects of the COVID-19 vaccines (particularly after the second dose of the Pfizer and Moderna vaccines). Most mild side effects resolve within a day or two and are not believed to be dangerous. If you are worried about side effects from the COVID-19 vaccines and your pregnancy, talk to your OB/GYN before getting the vaccine.

    Read more about potential side effects

  • I am breastfeeding. Should I get vaccinated?

    National and international experts, including the World Health Organization (WHO), suggest that any vaccine that makes its way into breast milk will be quickly inactivated when the milk is digested. At this time, there is no data regarding the safety of these new vaccines on breastfed infants. If you are breastfeeding, some of your COVID-19 antibodies that you make to develop immunity can naturally pass to your baby.

  • Will the COVID-19 vaccines affect my chance of getting pregnant in the future?

    There is no evidence that the vaccines affect future fertility.

  • What if I become pregnant between the first dose of the Pfizer or Moderna vaccine and the second dose?

    If you received a first dose of the Pfizer or Moderna vaccine, you can choose to either get the second dose during pregnancy or wait to get the second dose until after you have had your baby. Many individuals who have already had the first dose may choose to get the second dose, so that they will become immune during pregnancy.

  • I am planning pregnancy in the near future. Should I get vaccinated now or wait?

    The COVID-19 vaccines are not believed to affect your future fertility. Getting vaccinated before you get pregnant may prevent COVID-19 during pregnancy. It can also avoid the need for vaccination during pregnancy. Eighteen (18) people who were in the COVID-19 vaccination studies did become pregnant after vaccination. So far, those pregnancies are ongoing. We hope to learn more about their pregnancies soon.


  • Can children get the vaccine?

    The Pfizer vaccine is approved for youth ages 16 and older. The Moderna vaccine is approved for people 18 years of age and older. The initial trials of these vaccines were limited to these age ranges and did not include younger individuals.

    Teens who are 16 and older are eligible for the vaccine in Massachusetts, as of April 19. Eligible patients 16-17 years old who receive an invitation for the vaccine at a Mass General Brigham location need a waiver signed by a parent to receive the vaccine. 

    If you live in another state, please check your state’s information.

  • When will those 15 and younger be able to get a COVID-19 vaccine?

    We do not know when one or more of the vaccines might be approved for this age group. Children younger than 12 have not yet been included in trials.

    Children’s and adults’ immune systems are different and can produce different immune responses to vaccines. The vaccines need to be studied in children 15 and younger to make sure they are safe and that they work. Pfizer and Moderna have begun new vaccine trials that include children as young as age 12. Johnson & Johnson will first test its vaccine in children older than 12 and under 18 but has plans to begin a study that includes newborns and adolescents. Once there is data, the vaccines will through the same U.S. Food and Drug Administration (FDA) review process. The vaccines will be approved if the data shows they are safe and effective. It will likely take several months. 

  • Will children be vaccinated before the start of the 2021-22 school year?

    As these vaccines are not yet approved for people younger than 16 years old, it is unlikely most children will be vaccinated by the start of the next school year. However, teachers and school staff have the opportunity to be vaccinated. Teens aged 16 and 17 years may be vaccinated by the beginning of the school year.

Patients with cancer

Updated 4/16/21