Frequently Asked Questions

No. COVID-19 vaccines do not use the live virus that causes COVID-19. These vaccines work by using a harmless piece of spike protein from the virus causing COVID-19 to teach the body how to fight the virus that causes it. The body then gets rid of the harmless spike protein within a few days after vaccination. 

Although COVID-19 vaccines were developed quickly, research and development on vaccines like these have been underway for decades. All vaccine development steps were taken to ensure COVID-19 vaccine safety and effectiveness, including: 

  • Clinical Trials – All vaccines in the U.S. must go through 3 phases of clinical trials to ensure they are safe and effective.  
  • Authorization & Approval – Before vaccines are available to people, the U.S. Food and Drug Administration (FDA) must review data from clinical trials and approve vaccines that meet required scientific and safety standards.  
  • Tracking Safety Using Vaccine Monitoring Systems – Like every other vaccine approved for use in the U.S., COVID-19 vaccines continue to be monitored for safety and effectiveness. Hundreds of millions of people in the United States have safely received COVID-19 vaccines. CDC and FDA continue to provide updated information on the safety of U.S. authorized or approved COVID-19 vaccines using data from several monitoring systems.  

For more information on the safety of COVID-19 vaccines, please visit the CDC website,

Adults and children may experience some side effects from a COVID-19 vaccine, including pain, redness or swelling at the injection site, tiredness, headache, muscle pain, chills, fever, and nausea. These side effects are a normal part of your body developing protection against COVID-19. Serious side effects are extremely rare.

COVID-19 vaccination significantly lowers your risk of severe illness, hospitalization, and death if you get infected. Compared to people who are up to date with their COVID-19 vaccinations, unvaccinated people are more likely to get COVID-19, much more likely to be hospitalized with COVID-19, and much more likely to die from COVID-19.  

People who are up-to-date on their COVID-19 vaccinations may still get a COVID-19 infection after vaccination. However, staying up-to-date on your COVID-19 vaccinations means that you are less likely to get sick with COVID-19 and, if you do get sick, you are less likely to get severely ill or die. Staying up-to-date with COVID-19 vaccination also means you are less likely to spread the disease to others and increases your protection against new variants of SARS-CoV-2, the virus that causes COVID-19. 

COVID-19 vaccines are working very well to prevent severe illness, hospitalization, and death. However, public health experts are seeing reduced protection over time against mild and moderate disease, especially among certain populations, which is why vaccination recommendations and vaccines are updated. 

Scientists are monitoring how long COVID-19 vaccine protection lasts. Recent data shows that 1 dose of the updated COVID-19 vaccine better protects you against more serious illness, hospitalization, and death. People who have received the updated COVID-19 vaccine in recent months are better protected against severe illness from COVID-19 than those who have not gotten it. 

CDC recommends everyone stay up to date with COVID-19 vaccines for their age group: 

Some people can get additional doses of COVID-19 vaccine: 

  • People aged 65 years and older may get a 2nd dose of updated Pfizer BioNTech or Moderna COVID-19 vaccine 4 or more months after the 1st updated COVID-19 vaccine. 
  • People who are moderately or severely immunocompromised may get additional doses of updated Pfizer BioNTech or Moderna COVID-19 vaccine 2 or more months after the last updated COVID-19 vaccine. 

Talk to your healthcare provider about additional updated doses. 

The COVID-19 vaccines for children have the same active ingredients as the vaccines given to adults. However, children receive a smaller and more age-appropriate dose that is right for them. The smaller doses were rigorously tested and found to create the needed immune response for each age group, making it important for your child to get the vaccine made for their age group. 

You should get a COVID-19 vaccine even if you already had COVID-19. Getting a COVID-19 vaccine after you recover from COVID-19 infection provides added protection against COVID-19. You may consider delaying your vaccine by 3 months from when your symptoms started or, if you had no symptoms, when you received a positive test. People who already had COVID-19 and do not get vaccinated after their recovery are more likely to get COVID-19 again than those who get vaccinated after their recovery. Learn more about the benefits of getting a COVID-19 vaccine. 

No. You should wait to be vaccinated until after you complete your isolation period. People who have symptoms will end isolation at a different time than people who do not have symptoms. This also applies to people who have been vaccinated but get COVID-19 before getting any additional or booster doses. Additionally, you may consider delaying your next vaccine by 3 months from when your symptoms started or, if you had no symptoms, when you received a positive test. 

People who have had a known COVID-19 exposure should not seek vaccination until theirdesignated quarantine period has ended to avoid potentially exposing healthcare personnel and others during the vaccination visit.  

There is no recommended waiting period between getting a COVID-19 vaccine and other vaccines. You can get a COVID-19 vaccine and other vaccines, including a flu vaccine, at the same visit. Experience with other vaccines has shown that the way our bodies develop protection, known as an immune response, and possible side effects after getting vaccinated are generally the same when given alone or with other vaccines. 

Yes, the COVID-19 vaccine is recommended for people who are pregnant, breastfeeding, or trying to get pregnant now, as well as people who might become pregnant in the future. COVID-19 vaccination is recommended for people who are pregnant because the vaccine can prevent severe illness and death in people who are pregnant and protect their babies from severe infection. People who get infected with COVID-19 during the pregnancy period are more likely to deliver a preterm (earlier than 37 weeks) or stillborn infant and may also be more likely to have other pregnancy complications. 

COVID-19 vaccination during pregnancy helps: 

Learn more about vaccination considerations and the safety and effectiveness of COVID-19 vaccinations for people who are pregnant or breastfeeding. 

If you are pregnant and have received a COVID-19 vaccine, we encourage you to enroll in v-safe, CDC’s smartphone-based system that provides personalized health check-ins after vaccination. A v-safe pregnancy registry has been established to gather information on the health of pregnant people who have received a COVID-19 vaccine. 

Last Reviewed 10-18-2023.