Dr. Scott Atlas, the White House coronavirus task force adviser who has promoted the concept of herd immunity and criticized lockdowns and mask mandates, stepped down from his role in the outgoing administration Monday. Atlas joined the task force in August after being heavily featured in conservative media attacking COVID restrictions , and during his time on the task force he frequently clashed with Dr. Anthony Fauci, who has favored using public health measures to combat the pandemic rather than allowing it to overwhelm the entire country. Atlas delivered his resignation letter to President Donald Trump on Monday, and later posted it to Twitter. Atlas was nearing the end of a 130-day window in which he could serve as a special government employee, according to CNN . In his resignation letter Atlas said during his time with the White House the task force “identified and illuminated early on the harms of prolonged lockdowns, including that they create massive physical health losses and psychological distress, destroy families, and damage our children.” "I sincerely wish the new team all the best as they guide the nation through these trying, polarized times," Atlas wrote, presumably referencing the incoming administration of President-elect Joe Biden. COVID-19 may have been in the U.S. earlier than previously known A new government study of blood donations published Monday suggested that COVID-19 “may have been present in the United States in mid-December of last year, rather than January as previously believed.” The study looked at more than 7,000 blood donations made between December 17, 2019 and January 13 of this year, and found that 39 donations made from California, Washington, and Oregon contained coronavirus antibodies “as early as December 13-16.” The Chinese government first admitted that it was treating a rash of pneumonia cases of an unknown origin in Wuhan in late December, and in January said it was a new virus. Despite the evidence that the virus was in the United States earlier than previously known, the authors stressed that “widespread community transmission was not likely until late February.” The first case in the U.S. was confirmed on January 21 in Washington from a man who had recently returned from a trip to Asia that included a trip to Wuhan , and the first case of local transmission—meaning an infection in someone who hadn’t traveled overseas—was confirmed by the Centers for Disease Control and Prevention on February 26. Since then, 13.5 million people in the U.S. have been infected and more than 268,000 have died, according to Johns Hopkins University . The report also trumpeted the use of blood donations to study the virus, saying it will “inform allocation of resources and public health prevention interventions to mitigate morbidity and mortality associated with COVID-19.” The CDC will issue guidance on who should get the vaccine first With the rollout of the first vaccine doses potentially coming as soon as this month, a CDC advisory panel will meet today to issue recommendations on who should be prioritized to receive the vaccine. The CDC’s Advisory Committee on Immunization Practices will discuss the “allocation of initial supplies” of the vaccine Tuesday in Atlanta and then vote on recommendations. Healthcare workers and residents of long-term care facilities are expected to be at the top of the list, based on discussions at a meeting of the same committee last month . The committee has also indicated that essential workers, elderly people, and people with underlying medical conditions could follow. While the CDC is issuing recommendations, state and territorial governments will ultimately decide how to roll out their vaccines. Currently, local governments have been given just $200 million total by Congress to roll out the largest and most urgent immunization program in the history of the country. Pfizer submitted an application to the FDA for emergency use approval for its vaccine last month, and Moderna did the same Monday . Both companies have said their vaccines were around 95% effective in large-scale clinical trials, and Moderna has claimed that its vaccine was 100% effective in preventing serious cases of the disease.