The COVID-19 case rate for unvaccinated Santa Clara County residents is nearly four times higher than among those who have been vaccinated, according to a new public dashboard launched by the county's Public Health Department on Wednesday.

The new dashboard shows the seven-day rolling average of new daily COVID-19 cases among the overall population, among unvaccinated residents and among fully vaccinated residents. The case rates represent the number of cases on a given day per 100,000 county residents.

With the delta variant spreading in the Bay Area, health leaders in Santa Clara and San Mateo counties are highlighting the risks people take if they aren't vaccinated. And those numbers don't lie. The fully vaccinated have a case rate of 6.8 per 100,000 residents in Santa Clara County while the case rate soars among the unvaccinated to 25.3 per 100,000 residents, according to the data. Overall, the county average is 12.1, a far cry from the single-digit numbers from mid-June.

"The case rate per 100,000 residents for the unvaccinated has jumped from about 3 to more than 25 over the past month. The case rate among the vaccinated, while also increasing in recent weeks, is not experiencing as steep of a spike," according to a Santa Clara County press release issued Wednesday.

"The latest numbers reflect what public health officials have been echoing in recent weeks: the delta variant is fueling a surge in cases and the unvaccinated are at the highest risk of infections."

San Mateo County health leaders have also focused on the rising rates. They have set a goal of getting 90% of county residents vaccinated against COVID-19 and to achieve at least an 80% vaccination rate for every community by the end of December, they said during Tuesday's Board of Supervisors meeting.

The goal comes as the delta variant, which is far more contagious than previous strains, continues to pose a danger for unvaccinated people who can become seriously ill, county Health Chief Louise Rogers said. While some communities in the county have already reached or surpassed the health department’s goals, others still lag behind. Many of the least vaccinated also have the highest rates of infection, according to county health department data.

As of Aug. 4, the number of COVID-19 cases per day has doubled over the past two weeks from 41 to 89. More than 100 cases per day were recorded on eight days in July. The infection rate among unvaccinated people in the county is six times that of those who are vaccinated, she said. Unvaccinated individuals account for 95% of COVID-19 hospitalizations and deaths, according to the California Department of Public Health, Rogers noted.

In comparison, the number of "breakthrough" cases among residents who are fully vaccinated but who still tested positive for the virus represents less than 1% of all cases from December 2020 through July 14 for a total of 158 breakthrough cases, said Dr. Anand Chabra, San Mateo County Health's COVID-19 mass vaccination section chief.

Of residents ages 12 and older who are eligible for immunization, 89.2% have completed the vaccinations. The bottom quarter of residents in the state's Healthy Places Index, which measures health based on factors such as poverty, lags behind with only 76% having been vaccinated, Chabra said.

San Mateo County measures vaccination rates starting with those who are ages 10 and older. East Palo Alto has a 74.2% vaccination rate of residents who have at least one shot; North Fair Oaks is at 75.9%. In comparison, neighboring city Menlo Park has a 96.6% vaccination rate and Redwood City is at 85.6%, according to county dashboard data. Communities with vaccination rates lower than East Palo Alto and North Fair Oaks are mostly rural or unincorporated and are generally sparsely populated, including Moss Beach, El Granada, Loma Mar and Broadmoor. Economically advantaged communities, which have far lower infection rates, also have high vaccination rates, according to the county data. Atherton, Ladera, Emerald Hills and Woodside are all at or close to 100% vaccinated, for example.

Infection rates in these least vaccinated urban communities also continue to run higher than the surrounding area, despite multiple efforts to reach residents. Chabra said the county would continue to ramp up its vaccination outreach to the most impacted communities.

East Palo Alto has the highest percentage of its population having tested positive out of all cities in the county. County data shows a total of 4,654 residents, or 16%, have tested positive for COVID-19 through July 29. North Fair Oaks comes in second at 1,839 residents, or 12.7%. The other cities with highest infection rates — San Mateo, Redwood City, South San Francisco, Daly City, San Bruno, Pacifica and Menlo Park — have between 4.7% and 6.7% positive cases relative to their populations based on 2019 and 2020 U.S. Census data.

Over the last month, South San Francisco, East Palo Alto, Pacifica and San Bruno respectively have had the highest percentages of residents with new cases relative to their populations, according to county data.

Most people who have not been vaccinated said they aren't sure if the vaccines are safe, according to the Kaiser Family Foundation COVID-19 Vaccine Monitor, which surveys people across the U.S. The latest results of the ongoing survey were released on Wednesday. One-fourth of unvaccinated adults said it is "likely" they will get the COVID-19 vaccine before the end of the year, including 13% who say it is "very likely." The majority, 25% of unvaccinated participants, said it is either "somewhat unlikely" or "very unlikely" they will get a vaccination before the end of the year. Of those who said they want to "wait and see," 45% said it is "likely" they will get vaccinated by the end of the year.