What is a COVID-19 vaccine booster?

A COVID booster shot is an additional dose of a vaccine given after the protection provided by the original shot(s) has begun to decrease over time. Typically, you would get a booster after the immunity from the initial dose(s) naturally starts to wane. The booster is designed to help people maintain their level of immunity for longer.

What is a COVID-19 vaccine third dose?

A third dose of the mRNA COVID-19 vaccines (Pfizer or Moderna) is identical to the first two doses. It can help protect people with weakened immune systems who did not have a strong enough response to the first two doses of one of the mRNA vaccines. Such people can get a third dose as soon as 28 days after a second dose. The FDA has authorized, and the CDC recommends, that those with certain medical conditions that suppress the immune system get a third dose of the same brand of COVID-19 vaccine that they initially received.

What is the difference between the 3rd dose and the booster?

The 3rd dose is to increase the immune response of someone with a weakened immune system up to the level of the rest of the population. The booster is to create another immune response and “boost” up the antibody levels.

Booster dose recommendations

Booster doses are available for anyone ages 18 or older who got their second dose of the Pfizer-BioNTech or Moderna vaccine at least 6 months ago or their first dose of the Johnson & Johnson vaccine at least 2 months ago.

Recomendaciones de dosis de refuerzo

Las dosis de refuerzo están disponibles para cualquier persona de 18 años o más que haya recibido su segunda dosis de la vacuna Pfizer-BioNTech o Moderna por lo menos hace 6 meses o su primera dosis de la vacuna Johnson & Johnson por lo menos hace 2 meses.

Would a third COVID shot have to be the same brand of vaccine I got originally?

Yes, your third vaccine dose should be the same type (Pfizer or Moderna) you received when you were first vaccinated. The third shot can be given to you when it has been at least four weeks (28 days) since your second shot, if you are considered immunosuppressed based on the criteria determined by the CDC.


Eligible immunocompromised individuals are encouraged to contact their primary care physician or pharmacy to receive the booster vaccine.