COVID-19 Vaccinations: Third Doses Now Available for Immunocompromised in Santa Clara County

August 14, 2021  

Transplant recipients, cancer patients and those with immunodeficiencies at greater risk of COVID-19 infection and serious illness can receive a third dose of Pfizer or Moderna vaccine; this federal approval only extends to a very narrow segment of the overall population  

Santa Clara County, CA – County officials announced today that a third dose of COVID-19 vaccination is now available for people who have a compromised immune system, effective immediately. Eligible individuals are encouraged to contact their primary healthcare provider for consideration of the additional dose. Appointments can also be scheduled now through the County’s website, which also includes information about numerous drop-in vaccination sites throughout the county, including local pharmacies.  

This expansion of eligibility follows the decision by the Food and Drug Administration to extend emergency use authorization (EUA) on vaccines to allow an additional dose, as recommended by the Advisory Committee on Immunization Practices (ACIP) and approved by the Centers for Disease Control and Prevention (CDC).  

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. 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. 

“We have vulnerable immunocompromised populations who are again at risk because of the rapid spread and high transmissibility of the Delta variant,” said Dr. Jennifer Tong, Associate Chief Medical Officer for Santa Clara Valley Medical Center. “For those, a third dose of vaccine offers a substantial additional layer of protection from infection and serious illness.” 

A third dose is available for moderately or severely immunocompromised who have had either Pfizer or Moderna. The newly expanded FDA EUA does not extend to individuals who received the Janssen (Johnson & Johnson) vaccine. The additional dose will be matched to the initial vaccination type. The recipient must have completed the initial vaccination series 28 days or more before the third injection. 

A third dose is NOT authorized by the FDA for use in fully vaccinated people who are not moderately to severely immunocompromised, as defined by the CDC. People with diabetes, heart disease, or who are elderly are not considered to be moderately to severely immunocompromised unless they have another condition that causes them to be immunocompromised to the same extent as someone who had a solid organ transplant. Those unsure of whether they fall into this very narrow category of being moderately to severely immunocompromised should consult with their doctor or a medical professional.  

All County Health System mass vaccination sites will be able to accommodate the newly approved third doses for eligible individuals as of August 14, with community-based mobile sites to begin by mid-week next week.  

For the latest information about COVID-19 vaccinations in Santa Clara County, visit

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