Santa Clara County sees few breakthrough COVID hospitalizations

Despite concerns about breakthrough COVID-19 infections, the number of hospitalizations among vaccinated residents in Santa Clara County remains low—and is mostly driven by older residents and those with underlying health issues, county health officials say.

At county-run hospitals, only 12 of 52 patients with COVID-19 involve people who are fully vaccinated, which health experts say suggests breakthrough cases are rare.

Santa Clara Valley Medical Center, O’Connor Hospital, and St. Louise Regional Hospital treated approximately 40 unvaccinated people for COVID as of last week, county health officials told San José Spotlight, noting the unvaccinated patients include residents who skipped the vaccine because they previously caught the virus, as well as those who waited to get a first dose until after a family member got sick.

“These patients tend to be younger and have fewer co-morbidities,” a county official said. “Their hospitalizations are therefore more likely to have been preventable with the vaccine.”

Breaking through

In contrast, breakthrough cases—when a person is infected with COVID-19 despite being fully vaccinated—hover at nine patients. There are three other patients who tested positive for COVID, but admitted for other health issues. Of the nine breakthrough cases, one person received vaccination outside of the U.S and four people reported being vaccinated but couldn’t show proof, officials said.

That’s 12 vaccinated residents with COVID in county hospitals out of roughly 1.4 million vaccinated people living in Santa Clara County. By contrast, that’s 40 unvaccinated people with COVID in county hospitals out of roughly 500,000 unvaccinated residents.

In other words, roughly 1 in every 116,666 vaccinated residents are hospitalized for COVID versus 1 in every 12,500 unvaccinated residents.

“It’s a terrific number,” said Dr. Julie Parsonnet, an infectious disease doctor at Stanford University. “Especially when we have many more vaccinated people in the population than unvaccinated.”

Santa Clara County’s numbers reflect a national trend that continues to demonstrate the effectiveness of the vaccines, Parsonnet told San José Spotlight. Unvaccinated people are 29 times more likely to be hospitalized than those who are inoculated, according to a federal study published last week.

But those with weakened immune systems remain at risk of infection and hospitalization.

“I can say with great certainty that the vaccinated patients that we see are substantially older than the unvaccinated patients, and the great majority of them have underlying conditions that probably made the vaccine less effective,” she said.

Private facilities

The surge in COVID-19, driven largely by the Delta variant, is sending more residents to hospitals in Santa Clara County. The county has a 14-day average of 239 people who are hospitalized for COVID at public and private facilities, a significant jump from a local average of 38 cases in early July, according to state data.

The data provided by the county health officials doesn’t include the number of cases in private hospitals, such as Kaiser Permanente.

A Kaiser spokesperson told San José Spotlight the company doesn't have the data specifically for Santa Clara County, but its hospitals are already treating about two-thirds as many patients as the peak of the surge last winter.

"Over 85% of the patients in our northern California hospitals, including those in intensive care, are unvaccinated," the spokesperson said in a statement. "It is clear vaccination against COVID-19 prevents most infections and reduces severe illness from this virus, and reduces the need for hospitalizations."

'Wear masks'

While the number of breakthrough COVID-19 hospitalizations in Santa Clara County remains low, those numbers could rise, health experts say. And that is to be expected.

“As we approach 80% vaccination rate, a large chunk of cases that we see are going to be among people who are vaccinated just because they're just so much more common,” said Dr. George Rutherford, a professor of epidemiology UC San Francisco. “There's an inherent failure rate to any vaccine… it doesn't mean that things have gone bad.”

In California, more than 22.5 million people are fully vaccinated, according to state data. The state recorded 112,460 breakthrough cases—or 0.5%—between Jan. 1 and Aug. 29. Approximately 3,000 vaccinated people were hospitalized in the same period statewide.

As the Delta variant continues to cause infections across the county and beyond, residents should continue to mask up to prevent transmission—and those with health issues should consider getting a third vaccine dose, Rutherford said.

“We want people to wear masks if they're vaccinated just because there's so much virus circulating right now,” he said. “This is something that's in your hands: wear masks. And be careful when you're in crowds.”

Contact Tran Nguyen at [email protected] or follow @nguyenntrann on Twitter.