A staffer at the Santa Clara County Fairgrounds helps senior residents get to their vaccine appointment in San Jose, Calif. on April 26, 2021 (Jana Kadah/Bay City News)

Transplant recipients, cancer patients and people with immunodeficiencies can receive a third dose of the Moderna or Pfizer vaccine in Santa Clara County as of Saturday.

The decision follows the Food and Drug Administration’s recent emergency use authorization for additional doses of the Pfizer and Moderna vaccines.

People with diabetes, heart disease or the elderly are not authorized by the FDA to receive a third dose unless they have additional conditions that weakens their immune system “to the same extent as someone who had a solid organ transplant,” says a press release by the County of Santa Clara Public Health Department.

Those unsure of if they fall under the eligible category should consult with a medical professional, said the county.

About 2.7 percent of the U.S. population is considered immunocompromised, according to numbers from the Centers for Disease Control and Prevention. In these populations, infection rates are higher than healthy populations, and they’re more likely to have a severe case of 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.”

The new expansion does not extend to the Johnson & Johnson vaccine, and recipients must have had their vaccination series 28 days before the third dose. The booster shot must match up with the recipient’s initial vaccine series.

All county vaccination sites are available to administer the third dose starting August 14, and mobile sites will follow suit by mid-week next week. Appointments can be scheduled at sccfreevax.org.