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Answers to Your Questions About COVID-19 Vaccine Safety

What is an Emergency Use Authorization, and which vaccines are FDA approved?

Three vaccines – Pfizer, Moderna, and Janssen (Johnson & Johnson) – received Emergency Use Authorization (EUA) from the federal Food and Drug Administration. The Pfizer COVID-19 vaccine then received FDA approval.

Learn more about what this means – and other information about the vaccines – in their EUA fact sheets for recipients and caregivers.

These factsheets can be found at:

Is the Johnson & Johnson vaccine safe?

All COVID-19 vaccines are safe and highly effective; they provide high levels of protection against serious illness, hospitalization, and death. There is a risk of rare but serious conditions involving blood clots and low platelets (CDC), or Guillain Barré syndrome (where the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis), in people after receiving the J&J COVID-19 Vaccine. The chance of either of these happening is very low, and the benefits of vaccination outweigh these risks. Review the FDA’s Johnson & Johnson fact sheet for more information.

How do we know if the vaccine is safe?

It’s important to know that vaccines go through more testing than any other pharmaceuticals. First, small groups of people receive the trial vaccine. Next, vaccine is given to people with certain characteristics (e.g., age, race, and physical health). Then, vaccine is given to tens of thousands of people and tested for effectiveness and safety.

After that, the CDC’s Advisory Committee on Immunization Practices (ACIP) looks at the data to see whether the vaccine works and is safe. They give advice to the United States Food and Drug Administration (FDA). The FDA looks at the data and the advice from the ACIP and decides whether to approve the vaccine. The vaccine is only approved after all of these steps are done, and the experts are sure that it works and is safe.

Visit the CDC website for more information. 

How are the vaccines safe if they were developed so fast?

The timeline to develop a COVID-19 vaccine was sped up but never cut corners on safety. Here is how:

  1. We already had helpful information: The COVID-19 virus is a part of a coronavirus family that has been studied for a long time. Experts learned important information from other coronavirus outbreaks that helped them to develop the COVID-19 vaccine, so we weren’t starting from scratch.
  2. Governments funded vaccine research: The United States and other governments invested a lot of money to support vaccine companies with their work. Working together with other countries also helped researchers move quickly.
  3. A lot of people participated in clinical trials: Many people wanted to help by being in the vaccine studies. Companies didn’t need to spend time finding volunteers.
  4. Manufacturing happened at the same time as safety studies: Vaccine companies were able to make and store doses of vaccine at the same time as studies (called clinical trials) were happening to show that the vaccines were safe and effective. This meant vaccines were ready to be distributed once they were approved.

How is it safe if we don’t know the long-term side effects?

The Pfizer and Moderna COVID-19 vaccines are what experts call messenger RNA vaccines, or mRNA vaccines for short. The Janssen (Johnson & Johnson) vaccine is called a viral vector vaccine. Both types of vaccines have been studied in animal and human trials for years. On the other hand, COVID-19 has only been around for about a year and the long-term side effects of COVID-19 infection are mostly unknown and may be serious. Therefore, getting vaccinated is the best choice for long-term health and safety.

Experts will continue to track COVID-19 vaccine side effects. People in clinical trials will be tracked for 2 years. Other people who get the vaccine can use a tool called v-safe on their smartphones to quickly tell the CDC if you have any side effects after getting the COVID-19 vaccine. V-safe users can share information for up to one year after their vaccine. Learn more at cdc.gov/vsafe.

Do the COVID-19 vaccines have any side effects?

Some people may have side effects after being vaccinated, which are normal signs that your body is building protection. These side effects may affect your ability to do daily activities, but they should go away in a few days. The most common side effects are minor and include tiredness, headache, pain at the injection site, muscle and/or joint pain, chills, nausea and/or vomiting, and fever.

Can a COVID-19 vaccine make me sick with COVID-19?

No. The Pfizer, Moderna, and Janssen (Johnson & Johnson) vaccines do not contain the live virus that causes COVID-19. This means that a COVID-19 vaccine cannot make you sick with COVID-19. (source: Facts about COVID-19 Vaccines (cdc.gov). Therefore, if you test positive for COVID-19, even if you have gotten the vaccine, you would need to isolate.

Should someone with a history of allergies get the COVID-19 vaccine?

You should not get the Pfizer, Moderna, or Janssen (Johnson & Johnson) COVID-19 vaccines if you have a history of severe allergic reaction (also called anaphylaxis) to any ingredient in the vaccine. If you have a history of a severe allergic reaction to something else that’s not in the vaccine, discuss with your health care provider before receiving the vaccine.

Although there is a small chance that the COVID-19 vaccines could cause a severe allergic reaction, this would usually happen within a few minutes to one hour after getting the vaccine.

Everyone, even if they don’t have allergies, is monitored for at least 15 minutes after getting a COVID-19 vaccine.

What are the ingredients in the vaccine?

The vaccines do not contain eggs, gelatin, preservatives, or latex. COVID-19 vaccine fact sheets for recipients and caregivers list the ingredients of each vaccine. They can be found at:

I would like to have a baby one day. Is it safe for me to get a COVID-19 vaccine?

Yes. The CDC recommends COVID-19 vaccination for people trying to get pregnant now, or who might become pregnant in the future. There is no evidence that antibodies made following COVID-19 vaccination or that vaccine ingredients will cause any problems with becoming pregnant now or in the future. In fact, there is no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems in women or men. Learn more. 

Baystate Health patients:

Patients who have received their COVID-19 vaccine or booster within 4 weeks of their upcoming scheduled appointment for a screening breast mammogram or breast screening ultrasound need to reschedule their appointment by calling 413-794-2222.

Can someone who is pregnant or breastfeeding get a COVID-19 vaccine?

Yes. The CDC and American College of Obstetricians and Gynecologists recommend COVID-19 vaccination for people who are pregnant or breastfeeding. COVID-19 infection during pregnancy increases the risk of severe illness and preterm birth. Evidence about the safety and effectiveness of COVID-19 vaccination during pregnancy has been growing. Data suggest that the benefits of receiving a COVID-19 vaccine outweigh any known or possible risks of vaccination during pregnancy.

See our decision guide for pregnant people.

Are the COVID-19 vaccines safe for children?

At this time, the Pfizer vaccine is authorized for people ages 12 and older, and the Moderna and Janssen (Johnson & Johnson) vaccines are authorized for people ages 18 and older. Younger children and adolescents should not receive COVID-19 vaccination at this time.

Will a COVID-19 vaccine change my DNA?

No. The COVID-19 vaccines do not change or interact with your DNA in any way.

Vaccines teach our immune system how to fight against a specific virus. They work with the body’s natural defenses to safely develop immunity to disease. In order to do its job, the COVID-19 vaccine doesn’t need to go inside the nucleus of the cell, which is where our DNA is kept. This means the vaccine never interacts with our DNA in any way and has no way to change it.

At the end of the process, our bodies have learned how to protect against future infection. That immune response and making antibodies is what protects us from getting infected if the real virus enters our bodies. (Source: CDC)

Who were the vaccines tested on?

The safety of the Pfizer COVID-19 vaccine was evaluated in people 16 years of age and older in two clinical studies conducted in the United States, Europe, Turkey, South Africa, and South America. Overall, 50.6% of participants were male and 49.4% were female, 83.1% were White, 9.1% were Black or African American, 28.0% were Hispanic or Latino, 4.3% were Asian, and 0.5% were American Indian or Alaska Native. The safety of the Pfizer vaccine in younger adolescents was studied in 2,260 adolescents ages 12-15 in the U.S.

The safety of the Moderna COVID-19 vaccine was evaluated in people 18 years of age and older in the United States. Overall, 52.7% of participants were male, 47.3% were female, 79.2% were White, 10.2% were Black or African American, 20.5% were Hispanic or Latino, 4.6% were Asian, 0.8% were American Indian or Alaska Native, 0.2% were Native Hawaiian or Pacific Islander, 2.1% were Other, and 2.1% were Multiracial.

The safety of the Janssen (Johnson & Johnson) vaccine was evaluated in people 18 years of age and older in the U.S., Brazil, South Africa, Colombia, Argentina, Peru, Chile, and Mexico. Overall, 45% of participants were female, 55% were male, 58.7% were White, 19.4% were Black or African American, 45.3% were Hispanic or Latino, 3.3% were Asian, 9.5% were American Indian/Alaska Native 0.2% were Native Hawaiian or other Pacific Islander, 5.6% were from multiple racial groups and 1.4% were unknown races.

More information

Visit these frequently updated Centers for Disease Control and Prevention (CDC) web pages on COVID-19 vaccination: