Doctors investigate rare COVID breakthrough cases infecting vaccinated Californians

SAN FRANCISCO (KGO) -- California is seeing an increase in coronavirus cases after months of decline.

As of Monday, there were 3,200 new COVID-19 cases in California, and now, medical doctors are noticing some of the first numbers of COVID vaccine breakthrough cases.

ABC7 News reporter Luz Pena is part of the ABC7 News Vaccine Team, and spoke to UCSF infectious disease experts who say the vaccines continue to be the best defense against the virus, especially as the Delta variant spreads.

As the Delta variant takes hold, some of the first COVID-19 cases among the vaccinated population are being detected. According to the states data, 74 vaccinated California's have died, however, the report states it is unknown if the primary cause of death in these cases was COVID-19 or if there were other alternate causes.

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Luz Pena: "What have you noticed with these breakthrough cases?"

Dr. Luetkemeyer: "The majority of the cases have not been ill. Very few of them have been hospitalized and for most of them they have been mildly symptomatic and have gone to get better."

At Zuckerberg San Francisco General Hospital one of seven COVID patients was vaccinated. According to the latest state data, 20.4 million fully vaccinated individuals, 10,430 post-vaccination cases (0.051%) have been identified.

That's one in almost 2,000 vaccinated Californians reporting a breakthrough case.

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"The majority of the new cases that we are seeing right now in the United States are occurring unfortunately on unvaccinated people. 99% of the COVID related deaths are among unvaccinated people. That to me feels heartbreaking because those are preventable deaths," said Dr. Annie Luetkemeyer, Professor of Medicine and Infectious Diseases at UCSF.

UCSF' Dr. Luetkemeyer emphasizing those breakthrough cases could've been worse without the vaccine triggering a strong immune response.

"It causes the immune system to go to work. It causes antibody production to occur so that the antibodies can fight off the disease and it also causes cells that fight called T-cells to be activated to help fight off the disease," said Dr. Luetkemeyer.

The CDC reporting breakthrough cases in a small percentage of the vaccinated population and "no unexpected patterns have been identified."

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UCSF researchers are looking to see if there is a correlation between a persons immune system and their level of antibodies before a breakthrough.

"Some people who have breakthrough infections haven't even been sure if they had symptoms at all. Their symptoms have been so mild. They are so short lived and like a slight sore throat or a few days of a stuffy nose that they debated to even get tested," said Dr. Michael Peluso, UCSF Infectious Disease physician.

Dr. Peluso said they began noticing the small number of breakthrough cases after June right as the Delta variant intensified.

"We are fortunate that so many of us have been vaccinated because I think that what we will see over the next few weeks and months will be much better than what it would've been if the vaccine uptake would've been lower," said Dr. Peluso.

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