California Hospital Sees Staff COVID-19 Infections Drop To 'Single Digits' After Achieving Herd Immunity

As COVID-19 vaccinations speed up across the United States, a hospital in hard-hit California says its staff has achieved herd immunity. In December, when the pandemic was at its peak in the state, UC Davis Medical Center had 231 employees out because of COVID-19. 

On Wednesday, that number was just 10. 

More than 56 million vaccine doses have been administered in the U.S. so far, although the nation is still far from the herd immunity scientists say the country needs to be safe. At UC Davis however, more than 90% of the staff has received at least their first shot — and have achieved that threshold. 

UC Davis nurse Chasity Whitmer was delivering babies at the height of the pandemic. When the time came for her to be vaccinated, she told CBS News' David Begnaud that she hesitated.

"If I got the vaccine, would I get COVID? What would my side effects be? How long would it last?" Whitmer recalled wondering.

But with a husband who stays home and takes care of the kids, Whitmer told CBS News what changed her mind.

"I was orienting a relief charge nurse on my unit and we were kind of having a discussion," she said. "What happens if we got COVID? We wouldn't be able to work. We wouldn't have income, we wouldn't have health insurance. And so we kind of just talked amongst each other and boosted our confidence up and stood in line to get vaccinated."

She and more than 90% of the staff at UC Davis Medical Center in Sacramento have received at least one dose of the vaccine. 

That number is at 100% among the hospital's emergency physicians, said Dr. Nate Kuppermann, director of the emergency department.

Kuppermann said vaccinating the majority of employees has changed his ability to staff the ER, and that it felt like "this pressure lifted from our shoulders."

"So before the vaccine came out, on any given day, we would have between 100, 150 employees that were sick with COVID and were calling in sick who were not coming in," he said. "And now I think it's single digits. I mean, there's less than 10."

It is not just UC Davis' health system — across the University of California Health System, cases among health staff dropped from 431 per week to 171 per week. With fewer staff out sick, the strain on health care workers has dropped too.

Interim Employee Health Services Director Anne Tompkins said the data from UC Davis, and people's stories, are "a testament that the vaccine is truly working."

"We're gonna be OK," she said.

As for Whitmer, the nurse has gone from being a vaccine skeptic to an evangelizer — a few days after she received her second dose, Whitmer's husband, mother, three children and grandmother all tested positive for COVID-19. Only she and her grandfather did not — and are the only two in the family who have been vaccinated.

"My husband was extremely sick with COVID pneumonia, was here at the emergency department for nine hours. My grandmother spent 25 days in the hospital with COVID pneumonia and is still recovering on oxygen," said Whitmer. "It's not fun seeing your family members sick. It's very scary, being a nurse, watching them get sicker and sicker and whether to go to the hospital, whether to stay home."

Whitmer said reliving it made her emotional, because she did not know if her husband "would be one of the ones that would live or die."

One member of the CBS News team who was shooting video inside UC Davis said it was the calmest, most quiet hospital he has visited in months.

And while the staff at there are confident that they are all protected by the vaccine, they still mandate masks and social distancing at all times.