At least eight fully vaccinated Nevada health care workers tested positive for the coronavirus last month in a rare cluster of "breakthrough" cases, according to a report. 

In all, 11 coworkers were infected after an off-site pool party on June 7, the vast majority came down with the Delta variant, which is believed to spread more easily, according to the Las Vegas Review-Journal, citing emails obtained from the Southern Nevada Health District. 

Two out of the three who weren’t fully vaccinated had received at least one dose of the vaccine, the newspaper reported. 

Sunrise Hospital and Medical Center in Las Vegas said the employees recognized their symptoms and got tested and all of them have been able to return to work. 

The hospital conducted an investigation to make sure the temperature-sensitive vaccine hadn’t been stored properly and concluded there was no improper handling. 

CDC REPORTS 4,115 BREAKTHROUGH CASES COVID-19 CASES INVOLVING HOSPITALIZATIONS OR DEATHS 

"At the request of the health district, HCA Sunrise Hospital conducted a preliminary investigation of its vaccine administration and storage practices and found no evidence of improper storage or handling issues," health district representative Stephanie Bethel of the Southern Nevada Health District told the newspaper. 

The infected workers were all employees at the Sunrise Hospital and Medical Center in Las Vegas who had attended an off-site pool party. 

The infected workers were all employees at the Sunrise Hospital and Medical Center in Las Vegas who had attended an off-site pool party.  (Google)

Hospital CEO Todd P. Sklamberg told the Journal that no patients were exposed to the virus. 

"There were no exposures to our patients as our staff complies with all PPE guidelines, masking at all times and wearing face shields with all patient encounters," he said. 

Bethel added, "It is important to remember that no vaccines are 100 percent effective and breakthrough cases are expected. To date more than 2 million doses of COVID-19 vaccine have been administered in Clark County. The three vaccines currently available provide protection against serious illness in breakthrough cases."

Mark Pandori, director of the Nevada State Public Health Laboratory, called the delta variant and other new strains the coronavirus "Olympians."

"The viruses that are circulating in July aren’t the viruses that were circulating in February. Pandori said. "The ones that are circulating now have a better ability to get around vaccination."

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Cases have spiked in the state recently, mostly due to those who aren’t vaccinated, according to the newspaper

In the state, 54% of residents over 12 years old have received at least one dose of the vaccine, according to Nevada health data