Santa Clara County public health officials urged eligible residents Friday to get a COVID-19 vaccine booster dose following an update to federal guidance about who should get a booster and when.
As of Thursday, nearly 75,000 county residents have received a booster vaccine dose, according to county data.
While not all of the county's fully vaccinated residents are eligible for a booster, that total still equates to just 5.1% of the nearly 1.5 million people in the county who have completed their vaccination series.
In addition, only 39% of people ages 65 and up who are eligible for a booster have received one, according to the county. Roughly 257,000 residents ages 65 and older are fully vaccinated, per local data.
While the three available vaccines remain highly effective at preventing serious COVID-19 illness and death, public health officials at all levels have argued that preemptively boosting the immune responses of those at particularly high-risk for serious illness, such as older people and those who are immunocompromised, will maximize protection against existing and potential variants of the virus, which could become more contagious and even circumvent vaccine protections.
"What we now know about the vaccines is they're very safe and they're very effective and the protection has waned over time," county Health Officer and Health Director Dr. Sara Cody said. "And that's why boosters are now recommended, particularly for those who are at highest risk of hospitalization and death."
The Food and Drug Administration issued its approval Wednesday for booster doses for people who received the Moderna and Johnson & Johnson vaccines. Last month, the FDA also approved boosters for people who received the two-dose Pfizer-BioNTech vaccine.
Under guidance from the FDA and Centers for Disease Control and Prevention, everyone ages 18 and up who received the one-dose Johnson & Johnson vaccine should get a booster dose two or more months after their first shot.
Eligible groups who received their second Pfizer or Moderna dose six or more months ago should also get a third dose, according to health experts.
Those eligible groups include people ages 65 and older, adults living at long-term care facilities, adults with underlying medical conditions and adults with weakened immune systems.
"In Santa Clara County and across the state, the uptake of boosters is not what we anticipated," Cody said. "We anticipated a much swifter uptake in boosters. One possible explanation is that the public is confused about who should get a booster."
In addition, the FDA said it is safe and perhaps even more effective to "mix and match" booster doses by receiving a booster shot of a vaccine brand, such as Pfizer, that is different from the brand a person initially received.
County COVID-19 Vaccine Officer Dr. Marty Fenstersheib noted that in addition to those in the county who have yet to receive a booster dose, nearly 180,000 residents have yet to get vaccinated at all.
"Those people are going to be at the highest risk for infection and bringing more potential risk to others in the community," he said.
People who live, work or go to school in Santa Clara County can visit covid19.sccgov.org for information on where to get a booster shot, which are offered at many retail pharmacies and doctor's offices as well as several large-scale sites operated by the county.
Vaccines are available both via appointment and on a walk-in basis, at no cost and without requirements for insurance or immigration status.
Watch the county's press conference: