Q: What is the difference between a third dose and a booster dose?

A: A booster dose is given to certain populations who completed their primary series of Pfizer vaccine and are expected to have had a strong immune response but may have waning immunity over time. A third dose in the primary mRNA series is recommended for people with immunocompromising conditions who may not have had a robust immune response from two doses of vaccine. The main differences are:

Who qualifies for it (list of conditions below)

• Which vaccines are authorized

• Third dose for immunocompromised is authorized for both Moderna and Pfizer

• Booster doses for those who qualify is authorized only for Pfizer

• When you can get it

• Third doses for immunocompromised are administered at least 28 days after the second dose of Moderna or Pfizer

• Booster doses for those who qualify are administered at least six months after the second dose of Pfizer.

Q: Who can get a booster dose?

A: Anyone who previously received the Pfizer vaccine and who falls in one of the categories below can receive a booster dose, as long as it has been at least six months since the second dose: • Anyone 65 years old and older • Anyone who lives in a long-term care facility who is at least 18 years old • Anyone age 18-64 who has one of the following conditions:  • Overweight or obesity 

• Diabetes

• Long term (chronic) Kidney disease

• High blood pressure

• Long term lung disease like COPD

• Dementia

• Down’s syndrome

• Heart conditions


• A weakened immune system

• Liver disease o Pregnancy

• Sickle cell disease

• History of organ transplant

• History of smoking

• Stroke

• Substance use disorder

• Anyone age 18-64 who is at high risk for COVID-19 exposure due to their job as a:

First responder (healthcare workers, firefighters, police, congregate care staff)

Education staff (teachers, support staff, daycare worker)

Food and agriculture worker

Manufacturing worker

Corrections worker

U.S. Postal Service worker

Public transit worker

Grocery store worker

Where can I receive a booster or third dose?

You can receive it at your local pharmacy, health department, or from your primary care physician.

Where can I get more information?

For questions about vaccinations, boosters, and testing, call the COVID-19 hotline at 1(800) 889-3931. You can also email your questions to