On Wednesday, entertainment reporter Catt Sadler issued a COVID-19 warning on Instagram, encouraging her vaccinated followers not to get too comfortable.

The former E! has been fully immunized. The Delta version of the coronavirus was infected by a news correspondent, who warned that “the pandemic is very much NOT over.”

She captioned a photo of herself lying in bed, “Delta is relentless and highly contagious and grabbed ahold of me even after getting vaccinated.”

Sadler mentioned that she was caring for someone who had COVID, which they mistook for the flu. She wore a mask around the person despite being vaccinated.

“I assumed I would be fine,” she explained. “Well I’m not. I’m one of many breakthrough cases that we are seeing more of each and every day.”

Sadler described “not mild” symptoms such as a “throbbing” headache, two-day fever, congestion, and exhaustion, among others.

I assure you you don’t want to feel like this,” she wrote to her followers who had not been vaccinated. “Don’t let your guard down,” she advised to those who had been vaccinated.

The immunizations are not 100 percent effective against COVID-19, according to health officials, and breakthrough infections are always a risk.

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“That’s the scary part,” Hugh Cassiere, director of critical care services at North Shore University Hospital’s Sandra Atlas Bass Heart Hospital, told NBC. “Delta has such a high infectivity rate.”