RELATED: If You Got This Vaccine, Your Risk of COVID After Vaccination May Be Higher. Duff took to her Instagram Story on Friday to reveal that she’s been battling COVID despite being vaccinated. “That Delta … she’s a little b****,” she wrote, referring to the variant that now accounts for 98.8 percent of COVID cases in the U.S., according to the latest data from the Centers for Disease Control and Prevention (CDC). Duff went on to detail the four main symptoms she’s experienced: a bad headache, loss of taste and smell, sinus pressure, and brain fog. The Younger star didn’t reveal if any of her family members—husband Matthew Koma, 9-year-old son Luca, two-year-old daughter Banks, and five-month-old daughter Mae—had also contracted the virus, but she did say she was “happy to be vaxxed.” RELATED: If You’re Vaccinated, This Is the Tell-Tale Sign You Have COVID, Study Says. In the past month, celebrities have been coming forward with their breakthrough COVID experiences on social media. This week, Melissa Joan Hart, the child star best known for Clarissa Explains It All and Sabrina the Teenage Witch, revealed she also contracted COVID. Though she’s fully vaccinated, she suspects she caught the virus from one of her sons, who no longer have to wear masks in school. Hart told her Instagram followers that her case was “bad,” and cited feeling like she had a weight on her chest and difficulty breathing as her two main symptoms. Country star Reba McEntire also said that she had breakthrough COVID in a livestream on TikTok in early August. McEntire said she and her partner Rex Linn contracted COVID despite being fully vaccinated and as a result, she warned her fans: “You guys, please stay safe. Wear your mask. Do what you have to do. Stay home. … It’s not fun to get.” Former E! host Catt Sadler also got breakthrough COVID in July. “The pandemic is very much NOT over,” she told her followers on Instagram. “Delta is relentless and highly contagious and grabbed ahold of me even after getting vaccinated.” Sadler said she had a fever, “serious fatigue,” a “throbbing” headache, “extreme congestion,” and pus coming out of her eye. Another TV personality, Trading Spaces alum Genevieve Gorder, posted on Instagram in July that she tested positive for COVID months after receiving two doses of the Pfizer vaccine in March. “I am so grateful to be vaccinated because I know as a person who’s had asthma since I was a little girl—and two autoimmune [diseases] as an adult— I would be on that hospital table,” she told her followers. “I would be on the ventilator. I would be the one you were praying about.” RELATED: If You Got Pfizer, This Is When You’re More Likely to Get Breakthrough COVID. Early data in April from the CDC estimated that about .008 percent of vaccinated people in the U.S. were still contracting COVID, but recent numbers indicate breakthrough infections might be more common, The New York Times reported this week.ae0fcc31ae342fd3a1346ebb1f342fcb The Times collected data from seven states that are keeping particularly detailed records of breakthrough infections: California, Colorado, Massachusetts, Oregon, Utah, Vermont, and Virginia. In six of those states, vaccinated people made up 18 to 28 percent of new COVID cases over the course of the past several weeks. Another study, conducted by researchers at Imperial College London, looked at the results of more than 98,000 COVID tests taken between June 24 and July 12, when the Delta variant had become the dominant strain in the U.K. Results showed that people who had received two vaccine doses were half as likely to test positive for COVID-19. That’s a significant drop from a previous study conducted by Public Health England that found that the vaccine was 88 percent effective against the Delta variant in those who were fully vaccinated. And for more COVID news sent right to your inbox, sign up for our daily newsletter. While the CDC has stopped tracking more mild breakthrough cases, i.e. those that don’t result in hospitalization or death, they continue to keep tabs on more severe breakthrough cases, which are still very rare. As of Aug. 9, the CDC says more than 166 million people in the U.S. had been fully vaccinated, and during that time, the agency received reports from 49 U.S. states and territories of 8,054 fully vaccinated people contracting COVID and being hospitalized or dying as a result—that’s .005 percent of fully vaccinated Americans. “We don’t want to dilute the message that the vaccine is tremendously successful and protective, more so than we ever hoped initially,” Scott Dryden-Peterson, MD, an infectious disease physician and epidemiologist at Brigham & Women’s Hospital in Boston, told The New York Times this past week. “The fact that we’re seeing breakthrough cases and breakthrough hospitalizations and deaths doesn’t diminish that it still saves many people’s lives.” RELATED: 74 Percent of Vaccinated People Who Get Severe COVID Have This in Common.