Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
To maximize protection from the Delta variant and prevent possibly spreading it to others, get vaccinated as soon as you can and wear a mask indoors in public if you are in an area of substantial or high transmission.
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.

Key Things to Know About COVID-19 Vaccines

Key Things to Know About COVID-19 Vaccines

NOTICE: FDA expanded the use of a booster shot for COVID-19 vaccines in certain populations and authorized a single booster shot for Moderna and the Johnson & Johnson/Janssen vaccine. The Advisory Committee on Immunization Practices is meeting on Thursday, October 21, to discuss its recommendations for COVID-19 booster shots.

What You Need to Know

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COVID-19 Vaccine ChatBot

Use SmartFind chat tool to find answers to common COVID-19 vaccination questions.

Availability of Vaccines

COVID-19 vaccines are widely accessible in the United States. Everyone aged 12 years and older should get a COVID-19 vaccination as soon as possible.

COVID-19 vaccines are available for everyone at no cost. Learn more about how COVID-19 vaccines get to you.

Many doctors’ offices, retail pharmacies, hospitals, and clinics offer COVID-19 vaccinations. Parents, check with your child’s healthcare provider about whether they offer COVID-19 vaccination.

Learn how to find a COVID-19 vaccine.


COVID-19 vaccines are effective at protecting you from COVID-19, especially severe illness and death. COVID-19 vaccines can reduce the risk of people spreading the virus that causes COVID-19. If you are fully vaccinated, you can resume activities that you did before the pandemic. Learn more about what you can do when you have been fully vaccinated.

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Studies show that COVID-19 vaccines are effective, especially at keeping you from getting seriously ill even if you do get COVID-19. Learn more about the benefits of getting vaccinated.

COVID-19 vaccines teach our immune systems how to recognize and fight the virus that causes COVID-19. It typically takes 2 weeks after vaccination for the body to build protection (immunity) against the virus that causes COVID-19. That means it is possible a person could still get COVID-19 before or just after vaccination and then get sick because the vaccine did not have enough time to build protection.

People are considered fully vaccinated 2 weeks after their second dose of the Pfizer-BioNTech or Moderna COVID-19 vaccines, or 2 weeks after the single-dose Johnson & Johnson’s Janssen COVID-19 vaccine. To receive the most protection, people should receive all recommended doses of a COVID-19 vaccine. Learn more about who is recommended to get an additional dose or a booster dose.

People can sometimes get COVID-19 after being fully vaccinated. However, this only happens in a small proportion of people, even with the Delta variant. When these infections occur among vaccinated people, they tend to be mild.

Learn more about the effectiveness of COVID-19 vaccines.


COVID-19 vaccines are safe and effective. Vaccines cannot give you COVID-19. You may have side effects after vaccination. These are normal and should go away within a few days.

Millions of people in the United States have received COVID-19 vaccines, and these vaccines have undergone and continue to undergo the most intensive safety monitoring in U.S. history. This monitoring includes using both established and new safety monitoring systems to make sure that COVID-19 vaccines are safe. COVID-19 vaccines cannot give you COVID-19. Read more to bust myths and learn the facts about COVID-19 vaccines.

CDC has developed a new tool, v-safe, to help us quickly find any safety issues with COVID-19 vaccines. V-safe is a smartphone-based, after-vaccination health checker for people who receive COVID-19 vaccines. Learn how the federal government is working to ensure the safety of COVID-19 vaccines.

While COVID-19 vaccines were developed rapidly, all steps have been taken to ensure their safety and effectiveness.

You may have side effects after vaccination, but these are normal

After COVID-19 vaccination, you may have some side effects. These are normal signs that your body is building protection. The side effects from COVID-19 vaccination, such as tiredness, headache, or chills, may affect your ability to do daily activities, but they should go away within a few days. Learn more about what to expect after getting vaccinated.

Population Immunity

Population immunity, also known as herd immunity or community immunity,  means that enough people in a community are protected from getting a disease because they’ve already had the disease or because they’ve been vaccinated.

Population immunity makes it hard for a disease to spread from person to person. It even protects those who cannot be vaccinated, like newborns or people who are allergic to a vaccine. The percentage of people who need to have protection to achieve population immunity varies by disease.

We are still learning how many people need to be vaccinated against COVID-19 before the population can be considered protected.

As we know more, CDC will continue to update our recommendations for both vaccinated and unvaccinated people.

Variants and Vaccines

  • COVID-19 vaccines approved or authorized by the U.S. Food and Drug Administration (FDA) help protect against Delta and other known variants.
  • These vaccines are especially effective at keeping people from getting very sick or dying from COVID-19.
  • To maximize protection against the Delta variant and prevent possibly spreading it to others, you should wear a mask indoors in public if you are in an area of substantial or high transmission even if you are fully vaccinated.
  • We don’t know how effective the vaccines will be against new variants that may arise.

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For Healthcare and Public Health

Clinical and Professional Resources: Toolkits and resources for healthcare workers and public health professionals.