COVID-19 Vaccine Frequently Asked Questions | Boston Medical Center

COVID-19 Vaccine Frequently Asked Questions

We can help stop the spread of COVID-19 with vaccines.


Vaccination will help protect you and those around you from COVID-19.

By being vaccinated, wearing a mask, and staying at least 6 ft. away from others, we can help end this pandemic.

Vaccination will help protect you

The COVID-19 vaccines are very effective in preventing COVID-19, especially severe disease. And they don't just protect you. By getting vaccinated, you’ll also help keep your family and your community safe from COVID-19.

BMC is vaccinating patients who are eligible under MA state criteria. The vaccine is also available at other health care organizations and pharmacies as part of the nation-wide vaccination effort. 

We will continue to update this page as we learn more about COVID-19 vaccines.


Let’s fight COVID-19 together.

Frequently Asked Questions

Learn about how the COVID-19 vaccines work and when they might be available to you.

What is a vaccine?

A vaccine is a substance that can help protect you against specific diseases. Vaccines cause your immune system to make antibodies, which fight viruses and bacteria. If you get exposed to a disease you’ve been vaccinated against, the antibodies will fight the disease-causing bacteria or viruses before they make you sick. For more information on vaccines, visit the Centers for Disease Control.

How do COVID-19 vaccines work?

There are three different vaccines available. Of those, the Pfizer and Moderna vaccines are both mRNA vaccines. They work by telling our bodies to make a protein that then produces antibodies. These antibodies help protect you from the virus that causes COVID-19.

The Johnson and Johnson vaccine instead uses a virus vector, different from the COVID-19 virus, that cannot replicate in the human body. The virus vector delivers a protein code that tells your immune system to make antibodies, which then protect you from COVID-19.

When can I get the COVID-19 vaccine?

As of May 13, 2021, all adults 12 years of age and older in Massachusetts are eligible to get the COVID-19 vaccine. Individuals ages 12-18 can only get the Pfizer vaccine.

No appointment is needed to get your vaccine at one of BMC’s community vaccination sites. However, if you prefer, you can schedule your vaccine at one of these sites via this link. Some BMC clinics are also giving COVID-19 vaccines, if you prefer to get vaccinated by your doctor.

You can also get the vaccine at a state vaccination site, a local community site, or a site such as CVS or Walgreens; you can find more details here.

Is the vaccine free?

Yes. The federal government has committed to providing the vaccine at no cost to all individuals who want the vaccine. In Massachusetts, insurance companies and providers have agreed to provide the vaccine without out-of-pocket fees or co-payments. You do not need to have health insurance in order to get the vaccine.


Is BMC giving all available COVID-19 vaccines? Can I choose which I get?

We anticipate that BMC will continue to have supply of the Pfizer, Moderna, and Johnson & Johnson vaccines, and will be providing all three to patients and staff. All three are being distributed across the state of MA and the country.

Some important things to keep in mind about the three vaccines:

  • All of the available COVID-19 vaccines are highly effective and safe, and have been through a strict clinical review.
  • All available COVID-19 vaccines are very effective in preventing severe disease, hospitalization, and death related to COVID-19. You will not be able to choose which you receive; which one you get will depend on our supply of each at the time.
  • If you get the Pfizer or Moderna vaccine, your second dose must be the same type of vaccine you got in the first dose. You cannot get a Pfizer vaccine for the first dose and Moderna for the second or vice versa. Only one dose is needed for the Johnson & Johnson vaccine.

While there are differences between the currently available vaccines, the best vaccine to take is the one that is available to you first. Some of those differences include:

Manufacturer Type of Vaccine Overall Efficacy (in clinical trials)* Efficacy Against Hospitalization and Death (in clinical trials) Number of Doses Required Ages Approved For
Pfizer mRNA  95 percent 100 percent Two doses, 21 days apart 12 and older
Moderna mRNA  94 percent 100 percent Two doses, 28 days apart 18 and older
Johnson & Johnson Virus vector 67 percent 100 percent One  18 and older

* Because these clinical trials took place in different times under different conditions, these numbers are not directly comparable and do not represent a head-to-head comparison.

How are COVID vaccines given?

The vaccines are given as a shot in the upper arm.

The Pfizer and Moderna vaccines both require two doses. For the Pfizer vaccine, the second shot will be three weeks after the first. For the Moderna vaccine, it will be four weeks later. It’s important that you get both shots. If you don’t, you won’t be as well-protected from COVID-19 as you could be.

Only one dose is needed for the Johnson & Johnson vaccine.

Do you need to be a U.S. citizen to get the COVID-19 vaccine?

Anyone who lives in Massachusetts, regardless of immigration status, can receive a COVID-19 vaccination at a site in the state. You do not need to provide an ID or Social Security number to get the COVID-19 vaccine. Getting the COVID-19 vaccine will not have any negative impact on your chances of getting a green card.

Where can I find information from the FDA?

A fact sheet from the FDA can be found here, and is available in 20 additional languages on the FDA website.

How well do the vaccines work?

Learn about how successful the COVID-19 vaccine is at preventing COVID-19.

Does the vaccine keep me from getting COVID-19?

All approved COVID-19 vaccines are very effective in preventing COVID-19. While they helped prevent COVID-19 generally, they were particularly good at preventing severe cases of the disease. And in clinical trials, they all were 100 percent effective in preventing hospitalization and death related to COVID-19.

However, it’s important to keep wearing a mask and distancing because:

  • Not everyone will get the vaccine at once. Following public health guidelines will help protect anyone who hasn’t gotten the vaccine yet.
  • Although it’s not likely, it’s still possible to get COVID-19 after getting the vaccine, as no vaccine is 100 percent effective.
  • We’re not sure yet how long the vaccine will protect you from getting COVID-19.

How long does protection from COVID vaccines last?

We don’t know how long protection will last. The studies that are going on now will help to answer that question. You may have to get vaccinated again in the future.

How well do the vaccines protect against the new COVID-19 variants?

The current COVID-19 vaccines are expected to provide at least some protection against new virus variants because they work by prompting your immune system to respond broadly to the virus. Studies done in places like Israel, where much of the population has been vaccinated, show that the Pfizer vaccine does offer at least some protection against COVID-19 variants. In addition, the Johnson and Johnson vaccine was tested in South Africa, where it performed reasonably well during a period when a variant was circulating. However, we don’t yet know whether the vaccines will be as effective against the new variants as they were in clinical trials.

As we learn more, scientists are studying ways to make the vaccines more effective against COVID-19 variants if necessary, including booster shots, new vaccines that target multiple variants, and building on the mRNA platform used by the Pfizer and Moderna vaccines to make them more effective.

Are children ages 12-15 getting the same dose of vaccine as people over the age of 18?

Yes. Different doses were tested during clinical trials of the vaccine in people ages 12-15 and it was determined that using the same dose of the vaccine as we use for adults is both safe and effective for this age group.

Is the vaccine safe?

The COVID-19 has been through strict safety trials. Learn more about what this means.

Are COVID vaccines safe?

Yes. COVID-19 vaccines have gone through the same trials as other approved vaccines. The COVID-19 vaccines have met the high safety standards these trials set.

The clinical trial process for COVID-19 vaccines was much quicker than for other vaccines, but it was done just as carefully. More than 110,000 people took the different COVID-19 vaccines as part of clinical trials. And the Moderna and Pfizer vaccines build on many years of research into mRNA vaccines.

In addition, the clinical trials included 10-19 percent percent Black and 15-45 percent Hispanic/Latinx participants (depending on the study), which means vaccine safety was tested within a diverse group. There were no major safety concerns in any of the trials.

The COVID-19 vaccines were approved under emergency authorization because of how serious the pandemic is. It's likely that other vaccines will be approved this way. But the safety standards for emergency authorization are close to the same as the ones vaccines have to meet for regular authorization.

Expert groups are also continuing to look at the COVID-19 vaccine’s safety after people start to take it.

What are the side effects of COVID-19 vaccines?

Some people in the clinical trials did report side effects. However, these have generally been mild, and are a sign the immune system is working. Reported side effects include headaches, fatigue, chills, and soreness at the injection site. A small number of participants had a fever.

For some people, these side effects were worse after the second dose.

Side effects from a vaccine usually go away on their own within a few days. You can take an over-the-counter medicine such as acetaminophen or ibuprofen to manage side effects after the vaccine. However, it is recommended that you avoid taking these medications right before getting your vaccine, unless they have been prescribed to you.

If your side effects last more than 48 hours, speak to your doctor.

Have there been any serious adverse events after these vaccines?

There have been a small number of reports of severe stroke-like illness associated with low-platelet count after the Johnson & Johnson COVID-19 vaccine. This reaction is extremely rare and has been investigated by the CDC and FDA, who then lifted the pause they had put in place on this vaccine.

Cases of Bell's Palsy were reported in participants of the mRNA COVID-19 vaccine clinical trials but occurred at a rate lower than is seen in the general population and developed several weeks after vaccination. There is no evidence that these cases of Bell's Palsy were caused by vaccination.

A small number of severe allergic reactions have been reported after vaccination with both Pfizer and Moderna COVID vaccines and are being investigated. All reactions responded to treatment, and every vaccine site will monitor people for signs of an allergic reaction after vaccination.

Can I get COVID-19 from the vaccine?

No, you cannot get COVID-19 from the vaccine. The vaccine doesn’t actually contain the virus that causes COVID-19.

Can I spread COVID from the vaccine?

No. The current vaccines do not contain the virus that causes COVID-19, which means the vaccine itself won’t cause you to spread COVID-19.

Can I still spread COVID-19 after I get the vaccine, even if I don’t get sick?

While we know the COVID-19 vaccines can prevent severe COVID-19 infections, we do not yet know how effective the vaccines are in preventing asymptomatic infection, which is when you are infected with COVID-19 but don’t have any symptoms. It may be possible to still spread COVID-19 after getting a vaccine, so it is still important to wear masks and keep distances between people.

As people start to get the vaccines, researchers will be looking at how well they prevent asymptomatic infection.

Will the vaccine stay in my body or enter my DNA?

No. None of the vaccines enter or change your DNA, or stay in your body.

Does the vaccine affect fertility?

There is no evidence that the COVID-19 vaccine affects fertility. In the safety data from the Pfizer trial, the same proportion of people got pregnant in the vaccine group as the placebo group. Based on this, the vaccine is recommended even if you are planning to get pregnant soon.

How can I know this is safe for children if so few children were involved in the clinical trials?

Thousands of children got the COVID-19 vaccine in clinical trials, with no serious side effects reported. Side effects were similar to what older teenagers and adults have, and there were no allergic reactions or other serious reactions. The CDC and FDA take safety of vaccines very seriously, especially for children. Their careful research determined that these studies show the vaccines are safe.

I recently got a Johnson & Johnson vaccine. Should I be worried?

Right now, it looks like these specific types of blood clots are an extremely rare reaction. Nearly 9 million people have gotten the vaccine, and fewer than 30 adverse events of this type have been reported. BMC continues to strongly encourage all patients and community members to get vaccinated with whichever vaccine is available to them.

However, it’s important to talk to your doctor if you have any serious side effects. If you or a loved one received a J&J vaccine within the last three weeks and have any of the following symptoms, please contact your health care provider or go to the nearest emergency room:

  • Severe headache
  • Abdominal (stomach) pain
  • Leg pain
  • Shortness of breath

Please note, these are not the same flu-like symptoms, including chills and fatigue, or arm pain that may happen within 48 hours after the vaccine.

The reported adverse events all happened within three weeks of the individual receiving the J&J vaccine. Beyond that time, the risk of this type of clot appears to be extremely unlikely.

Should I get the vaccine?

COVID-19 vaccines were tested in diverse clinical trials. Read more about what that means for specific groups.

Do the COVID-19 vaccines work in Black and Latinx individuals?

More than 110,000 people took the different COVID-19 vaccines as part of clinical trials. In addition, the clinical trials included 10-19 percent percent Black and 15-45 percent Hispanic/Latinx participants (depending on the study), which means vaccine safety was tested within a diverse group.

Data from clinical trials showed that the vaccine has similar success rates in white, Black, and Latinx people.

Should I get the vaccine if I had COVID-19 already?

Yes. Experts recommend getting the vaccine even if you already had COVID-19, because we don't know how long having COVID-19 protects you from getting it again. As long as you're not currently in isolation with COVID-19 and no longer have symptoms, you can get the vaccine.

Can pregnant or breastfeeding people get the vaccine?

Although there are currently no data specifically on COVID-19 vaccine safety in pregnant and breastfeeding people, there is very low concern for safety issues, based on experience with other vaccines and the science of the COVID-19 vaccines.

Therefore, based on guidance by the FDA and the CDC, people who are pregnant or breastfeeding may choose to have the COVID-19 vaccine at BMC.

If you are pregnant or breastfeeding, please talk to your doctor about potential risks and benefits. This tool may also help you understand the potential risks and benefits. We have seen that pregnant people are at increased risk for severe COVID, which means that the benefits may outweigh the risks for many.

As the vaccine is given to more people, researchers are looking at the benefits and potential risks for pregnant and breastfeeding people.

Should I get the vaccine if I have allergies?

The FDA recommends that people who have severe allergies to any ingredient in the vaccines do not get this vaccine. In addition, they recommend that you should not get the second dose if you have a severe allergic reaction to the first dose. Everyone who gets the vaccine will be watched for 15 minutes after the injection to make sure they do not have any signs of an allergic reaction. People who have severe allergies to other vaccines or injectable medications will be watched for 30 minutes.

The vaccine does not contain any food products - including eggs - or metals.

Once you are able to get the vaccine, talk to your allergist if you have concerns.

Should I get the vaccine if I have sickle cell disease?

The Sickle Cell Disease Association of America recommends that people with sickle cell disease receive COVID-19 vaccination at this time.

People with sickle cell disease who get COVID-19 may have increased rates of disease complications, hospitalization, intensive care unit admission, and death. Given the high efficacy and safety reported in the vaccine trials, we believe that the benefit of receiving a COVID-19 vaccine greatly outweighs the risk.

My health condition isn’t addressed here. How do I know if the vaccine is safe for me?

People with certain health conditions, including diabetes, heart disease, obesity, were included in the vaccine studies. Therefore, we have evidence the vaccine is safe for people with these conditions. However, people who are immunosuppressed were not part of the trials.

When the FDA approves vaccines, they'll also give recommendations about who should or shouldn't get each vaccine. If you have concerns about whether or not you should get a COVID-19 vaccine when you're able to, talk to your doctor.

Do the vaccines work in older adults?

The available vaccines worked as well in older adults as it did in younger adults. In the Pfizer trial, for example, about 45 percent of participants were ages 56-85.

Can the vaccines be given to children?

Yes, The FDA approved the Pfizer vaccine for anyone over 12 years of age. The Moderna and Johnson & Johnson vaccines are approved for anyone over 18 years of age.

Studies of the COVID-19 vaccines in children younger than 12 are ongoing.

After Your Vaccination

Learn how to keep yourself and others safe after you're vaccinated.

What should I do if I have side effects?

Many people who have been vaccinated have reported side effects. For some people, these side effects were worse after the second dose. Most side effects are mild and go away within 48 hours.

If you have mild side effects that develop within 48 hours, such as feeling feverish but with a temperature below 101 F, injection site pain, chills, mild fatigue, mild muscle aches, or minor headaches, you do not need to stay home. You may use an over-the-counter pain reliever, such as acetaminophen or ibuprofen, to treat these symptoms.

If you have a fever above 101 F, severe muscle pain, or severe headaches, please stay home and call your primary care provider.

If you get an itchy rash that’s just around the spot you got your injection, you can treat it with 1% hydrocortisone cream (available over-the-counter) once or twice a day until it goes away.

How long does it take to build immunity after you get vaccinated?

You will have some protection as soon as 12 days after your first dose of vaccine. A person is considered fully vaccinated 14 days after their second dose of the Pfizer or Moderna vaccination or the one dose of the Johnson & Johnson vaccine.

Can I still spread COVID-19 after I get the vaccine, even if I don’t get sick?

We do not yet know how effective the vaccines are in preventing asymptomatic infection, which is when you are infected with COVID-19 but don’t have any symptoms. It may be possible to still spread COVID-19 after getting a vaccine, so it is still important to wear masks and keep distances between people.

Researchers are studying how well the vaccines prevent asymptomatic infection but the information is not available yet.

Can I stop wearing a mask and taking other precautions after I’m vaccinated?

No, you should continue to wear your mask and practice physical distancing even after you have been vaccinated.

Right now, we don’t know if people who have been vaccinated can spread COVID-19, because it wasn’t studied in the clinical trials. The vaccine also doesn’t protect you from COVID-19 right away. It takes up to two weeks after the second dose for you to be fully protected.

That means you should keep following all current guidance to protect yourself and others. This includes:

  • Wearing a mask.
  • Staying at least six feet away from others.
  • Avoiding crowds.
  • Washing your hands often.
  • Following state travel guidance.
  • Quarantining if you’re exposed to someone with COVID-19.


Can I visit older family members after they have been vaccinated, but before I have been vaccinated?

According to Centers for Disease Control guidelines for vaccinated individuals, visits between fully vaccinated people and unvaccinated people are low risk for the people who have been vaccinated. Therefore, as long as you are at low risk for severe COVID-19, it would likely be safe for you to visit people who have been vaccinated.

If some members of my household are vaccinated and others are not, is it safe to return to our normal life?

When deciding what activities are safe for your household to return to, the most important thing to keep in mind is the risk level of the people in the household you are not vaccinated. If the people who are not vaccinated are at higher risk of severe COVID-19, you should continue to follow all public health guidelines, including wearing masks when near people in other households and maintaining physical distance.

Keep in mind:

  • When unvaccinated people from multiple households gather, there is a higher risk of COVID-19 transmission. All people involved in gathers like this should wear masks, stay at least six feet from others, and visit outdoors or in a well-ventilated space.
  • Everyone is encouraged to avoid medium or large gatherings. Specific states also have regulations around gathering size. For example, in Massachusetts indoor gatherings are limited to no more than 10 people and outdoor gatherings are limited to no more than 25 people.
  • Vaccinated people should continue to wear masks and follow all other public health guidelines when outside the home.

What happens if you get COVID-19 after your first dose of an mRNA vaccine?

You may want to delay your second dose of an mRNA vaccine if you develop COVID-19 between your first and second dose. The optimal length of this delay is not known. At a minimum, you should not get the second dose until the date the second dose is due and until you are recovered completely from COVID-19.