Immunity after vaccination
It takes about two weeks for your body to build up initial protection after your second dose of the Pfizer or Moderna vaccines or the single dose of the Johnson & Johnson vaccine. Some people who are vaccinated will get sick, but vaccination greatly reduces the chance of hospitalization and death.
Even when you are vaccinated, you should:
Wear a mask. For more information, refer to Recommendations for Wearing Masks.
Wash your hands often.
Stay home if you are sick, especially if you have been around someone who has COVID-19. If you have symptoms of COVID-19, you should get tested. Learn more at CDC: Symptoms of COVID-19.
Do not visit people who have had close contact to someone with COVID-19 and are in quarantine.
If you travel, follow CDC requirements and recommendations at Travel During COVID-19.
Follow guidance specific to your workplace.
What about herd immunity
Herd immunity is also called herd effect, community immunity, population immunity, or social immunity. This is when most people in a population or group are immune to a disease. Being immune means they cannot get the disease because either they got a vaccine, or they already had the disease and cannot get it again, at least for a while.
When a lot of people are immune, it helps to protect other people in the population who are not immune. Having herd immunity can stop or slow the spread of disease because it is harder for the germ to find people who are susceptible to disease and make them sick.
We do not know enough about COVID-19 to be sure herd immunity is possible. This is a new disease, so there has not been enough time to fully study immunity yet. It is possible that even with most of the population vaccinated, COVID-19 will still be able to spread in the population but at a much lower level/rate.
People can become very sick, be hospitalized, and or even die from COVID-19. This is why we do not want to rely on herd immunity happening by causing illness in everyone. Vaccination lets a person's body develop protection against a disease without having to actually get sick and long COVID, hospitalization, or death.