COVID-19 Vaccine FAQ's

All information on this page has been created by health professionals from LCHC, MGB, MassLeague, and the CDC.  




Janssen (J&J)

Authorized for:

People age 18 and up

People age 16 and up

People age 12 and up


2 doses, a minimum of 28 days apart

2 doses, a minimum of 21 days apart

1 dose

Time to reach full protection

14 days after second dose

14 days after second dose

28 days after vaccination (1 dose only)

Vaccine Type



Viral Vector


For scheduling and booster 



Is the COVID-19 vaccine safe?

  • It’s important to know that vaccine go through more testing than any other pharmaceuticals. Before any vaccine is made available to the public, it must go through rigorous development and testing. Manufacturing is critical – every dose must consistently be high quality. Additionally, extensive testing in clinical trials is conducted to prove safety. First, small groups of people receive the trial vaccine. Next, vaccine is given to people with particular characteristics (e.g. age and physical health). Then, vaccine is given to tens of thousands of people and tested for effectiveness and safety.

    After that, the data is reviewed by the FDA which approves the vaccine, and by an independent board, CDC’s Advisory Committee on Immunization Practices (ACIP) which will make its recommendations for use. These bodies are the final safeguards for the public ensuring any vaccine is both safe and effective.

    Please visit the  CDC’s webpage for more information.

  • All of these vaccines are highly effective at preventing hospitalization and death.

How can a safe vaccine be ready so quickly?

  • For two main reasons. First, because of the pandemic, scientists all over the world cooperated on a single goal: find a vaccine as quickly as possible. Second, the U.S. government paid drug companies a lot of money — over $12 billion — so there was no financial risk for them to develop the vaccine. That meant that scientists could start each of the 4 stages of testing as soon as there was safety data from the last one. Creating new drugs is very expensive, around $1.3 billion per drug, so companies usually wait after each stage to figure out if the drug will pay for itself. For the COVID-19 vaccines, companies already knew the drug would be paid for, so they could go faster.

Can I get COVID-19 from the vaccine?

  • No. Both types of vaccines, mRNA and Viral Vector, do not contain any of the virus that causes COVID-19 and cannot give you COVID-19. They also cannot change your DNA in any way.

  • None of the vaccines are 100% effective, so there is still a very small chance you that could be fully vaccinated and get COVID-19. However, this would not be caused by the vaccine itself. The vaccines are still safe to get, and all of them will significantly lower your risk of getting sick COVID-19.

Was the vaccine tested on people like me?

  • Yes. The Moderna vaccine was tested on 30,000 pople, slightly more men than women, 10.2% of whom were Black and 20.5% Latinx.

  • The Pfizer vaccine was tested on 37,000, evenly split between men and women, 9% of whom were Black and 27% Latinx. Almost half of the people in the Pfizer trial had a condition such as obesity, diabetes, or heart disease. 

I always get sick from the flu shot, so vaccines are not good for me.

  • Vaccine side effects such as being tired, getting a fever, and having head or body aches are signs the vaccine is working and your body is building immunity. Isn’t it better to feel a little sick from the flu shot than to be one of the 12,000 – 61,000 people who die from influenza every year? And, isn’t it better to feel a little sick from the COVID-19 vaccine than to be one of the over half million Americans who have already died from the disease?

Will I need to be tested for COVID-19 before getting the vaccine?

  • No, a COVID-19 test is not needed before getting the vaccine.

Should someone who is COVID-19-positive receive the vaccine?

  • Not if they are symptomatic. Vaccination of people who are known to have COVID-19 should be delayed until they no longer have symptoms and have completion of the isolation period. Isolation period being defined as 10 days from symptom onset date + 24 hours symptom free or 10 days from testing positive for asymptomatic cases.

Should people who have had COVID-19 be vaccinated?

  • Yes, people who have previously had COVID-19 should be vaccinated. People who are within 90 days of recovering from COVID-19 may defer vaccination, if desired, because current evidence suggests reinfection is uncommon during this time. However, those people are able to be vaccinated within the 90 days as long as they are recovered. Talk to a medical provider to be sure.



I already had COVID-19. Do I still need the vaccine?

  • Yes. You can get infected with COVID-19 a second time. Scientists still don’t know how long natural immunity lasts. So it is safest for you and your loved ones if you get vaccinated. Please note that if you were treated with monoclonal antibodies or convalescent plasma, you should wait 90 days before getting vaccine.

How long after getting the COVID-19 vaccine does it take to be effective?

  • It typically takes a few weeks for the body to build immunity 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 get sick. This is because the vaccine has not had enough time to provide protection.

How long will immunity last?

  • Scientists don’t know yet. It may be a couple of years. If this is the case, people may need to be vaccinated every year, as is done with influenza.

Once I get the vaccine, can I still get COVID-19?

  • Yes. The vaccines are extremely effective, but a small percentage of people immunized may still get the virus. You don’t know how effective if will be for you. You should do everything you can (including continuing to mask, wash your hands, and socially distance) to reduce your risk of getting the virus and passing it on to others.

Does the vaccine stay in my body?

  • No. The vaccine trains your body to recognize the virus and kill it. As the vaccine trains your body, the material in the vaccine itself it destroyed.

Do I still need the vaccine if I have strong immunity already, or I use natural remedies?

  • It’s great that you are already healthy. But, COVID-19 is a new virus that your body hasn’t encountered before. Getting the vaccine will train your body’s immune system to recognize and kill the virus if you are exposed to it.

Is it true that most young / healthy people don’t need the vaccine because if they get COVID-19, it won’t be as serious?

  • No. Some young and healthy people have very serious cases of COVID-19 and have even died from it. Others don’t even realize they have it. These people are actually the ones who spread COVID-19 the most. Scientists think about 60% of cases are caught from someone without symptoms. So, even if you are young and/or healthy, getting the vaccine will stop the virus from spreading to others, including older family members and those with health conditions.


Side-Effects / After Vaccination

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

  • It may hurt a little were you got the shot in your arm. You may also be tired, get a fever, and have head or body aches. These side effects are good! They are signs that the vaccine is working and your body is building immunity. Very rarely, a person has an allergic reaction to the vaccine right after getting it. To keep these people safe, healthcare providers have patients wait 15 – 30 minutes before leaving the vaccination area.

  • Most side effects will go away withing just a few days. Most people experience stronger side effects (e.g. more muscle fatigue) after the second dose than after the first dose.

Once I’m vaccinated, can I stop wearing a face mask and stop physical distancing?

  • No. You should continue to wear a face mask and practice physical distancing because not everyone is vaccinated at the same time, and research still doesn’t show yet if the vaccine totally stops you from spreading COVID-19. You should also continue to wash your hands frequently.

  • Infection control experts will let the public know when it is safe to modify or stop these safety measures.

I got the vaccine over 2 weeks ago, but I feel symptomatic. Should I get a COVID-19 test?



If I have a have a history of allergies with vaccines, can I still get the COVID vaccine?

  • Most people with a history of allergic reactions can still get the COVID vaccine. Consult an allergist and talk to your healthcare provider before scheduling your vaccination appointment.

Do the COVID vaccines contain egg, gelatin, or latex?

  • No.

Do the vaccines have any non-halal or non-kosher ingredients?

  • No, the vaccines do not include any pork, blood, or egg products.



If I am pregnant or lactating, should I still get the vaccine?

  • Yes. Vaccination, especially with vaccines like these that do not contain any live virus, is considered a safe and routine part of prenatal care. If you have specific concerns, you should talk to your OB/GYN.

Can the COVID-19 vaccine induce a miscarriage?

  • No. There is no data to suggest that the COVID-19 vaccines cause miscarriage.

Can I get the vaccine if I am breastfeeding?

  • Yes. Any vaccine that makes it into the breast milk is likely to be quickly inactivated when the milk is digested.



Are the vaccines safe for children?

  • Currently, the Pfizer vaccine is approved for youth ages 16 and older. The Moderna vaccine is approved for people 18 years of age and older. Children younger than 12 have not yet been included in clinical trials. It is not yet known when the vaccine might be approved for this age group.


Where does my information go?

Will I have to pay for the vaccine?

  • The vaccine is being provided free of charge to all individuals by the federal government. Insurance companies are also committed to not charging any out-of-pocket fees or co-payments related to COVID-19 vaccine administration, and all health care provider sites that receive COVID-19 vaccine must agree to not charge patients any out-of-pocket fees or deny anyone vaccination services.

Can undocumented immigrants receive the vaccine for free?

  • Yes. The vaccine itself is free for all Massachusetts residents. Health insurance (including Medicare and Medicaid) will cover the cost of administering the vaccine. For patients without health insurance, health care providers may request reimbursement from the federal government for the cost of administering vaccine to undocumented immigrants.

Can getting the COVID-19 vaccine affect my immigration status in any way?

  • It’s important that everyone get vaccinated, including immigrants, regardless of their status. The federal government will not impose any immigration consequences for getting the COVID-19 vaccine. This included being considered a pulice, even if you get it through a program like Medicaid. Federal and state laws require that healthcare providers keep patients’ personal information confidential.

Does the vaccine have something in it to track or control people?

  • The COVID-19 vaccine does not stay in your body, and even for the time it is in your body there is nothing in it that can track or control you. Getting the vaccine trains your body’s immune system to recognize a spike on the virus and kill any viruses with it. In that training process, all the original material from the vaccine is destroyed. To make sure residents stay healthy, Massachusetts does keep track of all immunizations in a confidential database. By law, only healthcare providers and public health officials can see it.

If I get the vaccine, will I be part of an experiment without my consent?

  • By law, no one can include you in an experiment without explaining the study and getting your written permission. The laws were passed in the 1970’s after some shameful history. In the 1930’s, the Tuskegee Project signed up 400 Black men with syphilis, telling them they would get health services. They didn’t tell them they were doing research to see what happened when the disease was left untreated. In the 1950’s, in Puerto Rico, poor, young women were given birth control, but not told about the possible side effects. The laws that not protect human subjects require researchers to tell people what they are doing and get their informed consent. They also require that special committees review every study.

Further Resources for Frequently Asked Questions