What we know
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 in a few days.
Millions of people in the United States have received COVID-19 vaccines, and these vaccines have undergone 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. Learn 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.
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 in a few days. Learn more about what to expect after getting vaccinated.
What we know
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.
What we are still learning
We are still learning how many people have 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
FDA-authorized COVID-19 vaccines help protect against Delta and other known variants.
These vaccines are effective at keeping people from getting COVID-19, getting very sick, and dying.
To maximize protection from 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.
What we know
COVID-19 vaccines are effective against severe disease and death from variants of the virus that causes COVID-19 currently circulating in the United States, including the Delta variant.
Infections happen in only a small proportion of people who are fully vaccinated, even with the Delta variant. When these infections occur among vaccinated people, they tend to be mild.
If you are fully vaccinated and become infected with the Delta variant, you might be able to spread the virus to others.
People with weakened immune systems, including people who take immunosuppressive medications, may not be protected even if fully vaccinated.
For Healthcare and Public Health
Clinical and Professional Resources: Toolkits and resources for healthcare workers and public health professionals.