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COVID-19 Status Update for 09/24/2021

Marin County COVID-19 Status Update for September 24, 2021 includes Boosters Ok’d for Older Adults, At Risk Groups; Healthcare and Care Facility Staff Advised to Get Flu Shot; and updated … Read More

Boosters and Third Doses


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Updated September 24, 2021:

Federal and State regulatory agencies have provided authorization for certain groups to receive booster or third doses.  This page offers clarification on who is eligible to receive an additional dose of the COVID-19 vaccine, the difference between third doses and booster shots, and where to find one.

Additional authorizations to provide booster doses to a wider group of people (Moderna and Johnson and Johnson recipients) are expected to be considered by CDC later this year. We will update this page as those authorizations are made.

What is the Difference Between a 3rd Dose and a Booster?



Who qualifies for a booster dose?

A Pfizer/BioNTech booster shot is recommended for people who received the Pfizer Covid-19 vaccine series at least 6 months ago, and are:

In addition, the CDC authorized a booster shot for those who received Pfizer/BioNTech Covid-19 vaccine series at least 6 months ago, and (a) are aged 18-49 with underlying medical conditions, or (b) are aged 18-64 and at increased risk for COVID-19 exposure and transmission because of occupational or institutional settings.

At this time, boosters are not authorized for Moderna or Johnson and Johnson vaccine recipients, but are expected to be considered by CDC later this year.


Who qualifies for a third dose?

The CDC recommends an additional dose of COVID-19 vaccine for moderately to severely immunocompromised people. This includes people who have completed a vaccination series with  Pfizer or Moderna and have:

  • Been receiving active cancer treatment for tumors or cancers of the blood
  • Received an organ transplant and are taking medicine to suppress the immune system
  • Received a stem cell transplant within the last 2 years or are taking medicine to suppress the immune system
  • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Advanced or untreated HIV infection
  • Active treatment with high-dose corticosteroids or other drugs that may suppress your immune response

Your additional dose must be administered at least 28 days after your vaccination series has been completed and must be the same vaccine as previous doses (e.g., you should not receive a Pfizer booster/third dose if your original series was Moderna and vice versa).  Johnson & Johnson third doses are not available at this time, but are expected to be considered by CDC later this year.

Why are third doses limited to such a small group?

The CDC estimates that about 2.7% of the population of the United States is immunocompromised, including organ transplant recipients, people undergoing cancer treatment, and those with other immunodeficiencies. In Marin County, this represents approximately 10,000 people. This population is more likely to become infected with COVID-19, even after vaccination, compared with similarly vaccinated but otherwise healthy individuals. They are also more likely to become severely ill due to COVID-19.


Where can I access a booster or third dose?

Many vaccine providers in Marin County are providing third doses and boosters to people who are eligible.


Pharmacies are a primary access point for booster shots and third doses in Marin County. Approximately 30 local pharmacy locations are providing booster and third doses to people who qualify. Click on a link below for more information.

Your healthcare provider:

Your health care provider is in the best position to know whether you will benefit from a booster shot or third dose. Providers who offer regular vaccinations (e.g., flu, pneumovax, shingles) should provide eligible patients with COVID-19 booster vaccines as capacity allows.

Public Health:

Marin County Public Health is providing third dose and booster shots at its vaccination locations as supply allows. Appointments are required for third doses and booster shots. Visit our Vaccine Finder for a list of locations.

Booster Clinic for Older Adults

Safeway Pharmacies and Marin County Public Health are partnering to offer a booster dose vaccine clinic dedicated to older adults, age 75 & older, who received the Pfizer Covid-19 vaccine series at least 6 months ago.  The clinic is intended to ensure booster dose access based on evidence of waning immunity and higher risk of mortality in this age group.

The enhanced booster dose clinic will begin on Wednesday, September 29 at the Northgate Shopping Center.  Appointments are strongly encouraged, but a limited number of walk-ins will be allowed each day as supplies last.  Vaccine seekers will need to bring their vaccine card and proof of age (e.g., ID Card).