Are COVID-19 vaccine boosters or extra shots recommended?

By Mayo Clinic Staff

May 21, 2022

Key takeaways


An additional primary shot of a COVID-19 vaccine is recommended for people who are vaccinated and might not have had a strong enough immune response. In contrast, a booster dose is recommended for people who are vaccinated and whose immune response weakened over time. Research suggests that getting a booster dose can decrease your risk of infection and severe illness with COVID-19.

People who have a moderately or severely weakened immune system should get an additional primary shot and a booster shot.

The CDC recommends additional primary shots and booster doses of COVID-19 vaccines in specific instances:

  • Additional primary shot. The CDC recommends a third dose of an mRNA COVID-19 vaccine for some people with weakened immune systems, such as those who have had an organ transplant. People with weakened immune systems might not develop enough immunity after vaccination with two doses of an mRNA COVID-19 vaccine or one dose of the Janssen/Johnson & Johnson COVID-19 vaccine. An additional shot using an mRNA COVID-19 vaccine might improve their protection against COVID-19.

    The CDC now recommends that children ages 5 through 11 who have moderately or severely weakened immune systems should get an additional primary shot of the Pfizer-BioNTech COVID-19 vaccine.

    The additional primary shot should be given at least four weeks after a second dose of an mRNA COVID-19 vaccine or one dose of the Janssen/Johnson & Johnson COVID-19 vaccine. The additional shot should be the same brand as the other two mRNA COVID-19 vaccine doses that were given. If the brand given isn’t known, either brand of mRNA COVID-19 vaccine can be given as a third dose.

  • Booster dose. A single booster dose is recommended for people age 5 and older after getting two doses of an mRNA COVID-19 vaccine or one dose of a Janssen/Johnson & Johnson COVID-19 vaccine.

    People ages 5 and older can get a single booster dose if they been given both doses of the Pfizer-BioNTech COVID-19 vaccine and at least five months have passed. Children ages 5 to 17 should only get the Pfizer-BioNTech COVID-19 vaccine booster.

    If you are age 18 or older, have been given both doses of the Moderna COVID-19 vaccine and it’s been at least 5 months, you should get a single booster dose.

    If you are age 18 or older, have been given one dose of the Janssen/Johnson & Johnson COVID-19 vaccine and it’s been at least 2 months, you should get a single booster dose.

    The Pfizer-BioNTech or Moderna COVID-19 vaccine boosters are preferred in most situations.

    Pregnant women can also get a COVID-19 booster shot.

    If you have a weakened immune system, had two doses of an mRNA COVID-19 vaccine and an additional primary shot, and it’s been at least three months since the additional shot, get a single booster dose. An mRNA COVID-19 vaccine is preferred.

    If you have a weakened immune system, had one dose of the Janssen/Johnson & Johnson COVID-19 vaccine and an additional primary shot of an mRNA COVID-19 vaccine, and it’s been at least two months since the additional shot, get a single booster dose. An mRNA COVID-19 vaccine is preferred.

  • Second booster dose. A second booster dose of an mRNA COVID-19 vaccine is recommended for certain people who have a weakened immune system and people age 50 or older. This second booster dose can be given to those eligible four months after a first booster dose of any authorized or approved COVID-19 vaccine.

More about COVID-19 boosters and extra shots