Sister Deirdre "Dede" Byrne, POSC. / EWTN News NightlyWashington D.C., Mar 11, 2022 / 08:10 am (CNA).Sister Dierdre Byrne, a Roman Catholic nun who is also a physician-surgeon and a retired U.S. Army colonel, is suing Washington, D.C. for denying her a religious exemption to its COVID-19 vaccination mandate for health care workers.Known as "Sister Dede," Byrne was an Army doctor who did a three-month tour in Afghanistan as a reservist prior to joining the Sisters of the Little Workers of the Sacred Heart. In Washington, she serves as medical director of her convent's free medical clinic. She also operates an abortion pill reversal ministry in the city.She objects to the mandate on moral grounds because all three vaccines approved for use in the United States "have been tested, developed, or produced with cell lines derived from abortions," which she says violates her Catholic beliefs, according to a statement from one of her attorneys, Christopher Ferrara, special counsel for t...