President-elect Joe Biden announced his health care team on Tuesday, and committed to vaccinating 100 million Americans against the coronavirus during his administration’s first 100 days.

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At an event from Delaware to introduce his pandemic response team on Tuesday, Biden laid out his top three priorities for the start of his new government. He repeated his previous calls for all Americans to wear masks for 100 days to prevent the spread of the virus and said he’d mandate doing so in federal buildings and on public transportation, while also making the new promise to distribute 100 million vaccines shots over the same period.

Biden also said he believed that the virus can be brought under enough control to reopen “the majority of schools” within his first 100 days.

Those pledges came on the same day as the U.S. surpassed 13 million confirmed coronavirus cases, and the pandemic’s death toll reached record levels across the nation.

Biden announced he has chosen Dr. Rochelle Walensky, a Harvard infectious disease expert, to lead the Atlanta-based Centers for Disease Control and Prevention. Biden also has picked California Attorney General Xavier Becerra to be his health secretary. Other members of Biden’s health team include Dr. Marcella Nunez-Smith as the COVID-19 equity task force chair and Dr. Anthony Fauci as chief medical adviser.

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Businessman Jeff Zients was named as Biden’s White House coronavirus coordinator. An economic adviser to former President Barack Obama, Zients also led the rescue of the HealthCare.gov website after its disastrous launch in 2013. And former Surgeon General Vivek Murthy, a co-chair of Biden’s coronavirus task force, is returning to the position with, what Biden described as, additional responsibilities.

Biden’s choices for his health care team point to a stronger federal role in the nation’s COVID-19 strategy, restoration of a guiding stress on science and an emphasis on equitable distribution of vaccines and treatments. Biden is aiming to leave behind the personality dramas that sometimes flourished under President Donald Trump and hopes to return the federal response to a more methodical approach, seeking results by applying scientific knowledge in what he says will be a transparent and disciplined manner.

“We are still going to have a federal, state and local partnership,” commented Dr. Georges Benjamin, executive director of the nonprofit American Public Health Association. “I just think there is going to be better guidance from the federal government and they are going to work more collaboratively with the states.”

By announcing most of the key positions in one package, Biden is signaling that he expects his appointees to work together, and not as lords of their own bureaucratic fiefdoms.

“These are not turf-conscious people,” said Drew Altman, CEO of the nonpartisan Kaiser Family Foundation, a clearinghouse for health care information and analysis. But “it’s up to the administration to make it an effective team.”

Walensky, a recognized HIV/AIDS expert, got her coronavirus experience first hand as chief of infectious diseases at Massachusetts General Hospital in Boston during the first wave this spring.

“She was a real leader when it came to COVID,” said Dr. Rajesh Gandhi, an infectious disease physician at Mass General. “She organized infection control policies within the hospital, she organized treatment studies, she was organizing testing and leading testing.”

Biden’s selection of Yale’s Nunez-Smith is being read as a sign that his administration will work for equitable distribution of vaccines and treatments among racial and ethnic minorities, who have suffered a disproportionately high toll of COVID-19 deaths.

That challenge faces widespread skepticism among minorities that the health care system has their best interests in mind.

If confirmed, Becerra, 62, will be the first Latino to head the Department of Health and Human Services, a $1 trillion-plus agency with 80,000 employees and a portfolio that includes drugs and vaccines, leading-edge medical research and health insurance programs covering more than 130 million Americans.

Becerra, as the state of California’s top lawyer, has led the coalition of Democratic states defending “Obamacare” from the Trump administration’s latest effort to overturn it, a legal case awaiting a Supreme Court decision next year.

A former senior House Democrat, Becerra was involved in steering the Obama health law through Congress in 2009 and 2010. At the time, he told reporters that one of his primary motivations was having tens of thousands of uninsured people in his Southern California district.

Becerra has a lawyer’s precise approach to analyzing problems and a calm demeanor.

But overseeing the coronavirus response will be the most complicated task he has ever contemplated. By next year, the U.S. will be engaged in a mass vaccination campaign, the groundwork for which has been laid under the Trump administration. Although the vaccines appear promising, and no effort has been spared to plan for their distribution, it’s impossible to tell yet how well things will go when it’s time to get shots in the arms of millions of Americans.

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But the core components of HHS are the boots on the ground of the government’s coronavirus response. The Food and Drug Administration oversees vaccines and treatments, while much of the underlying scientific and medical research comes from NIH. The Centers for Disease Control and Prevention takes the lead in detecting and containing the spread of diseases. The Centers for Medicare and Medicaid Services provides insurance coverage for more than 1 in 3 Americans, including vulnerable seniors, as well as many children and low-income people.

Becerra’s experience running the bureaucratic apparatus of the California attorney general’s office, as well as his success working with Republicans, helped seal the pick for Biden, said a person familiar with the process but not authorized to comment publicly. Becerra had worked with Louisiana’s Republican attorney general to increase the availability of the COVID-19 drug treatment Remdesivir in their states. He’s also worked closely with other Republican attorneys general on legal challenges against opioid manufacturers.

Early in California’s coronavirus response, Becerra defended broad shutdowns Gov. Gavin Newsom had put in place to curtail the pandemic, including limits on religious gatherings. Three churches in Southern California had sued Newsom, Becerra and other state officials because in-person church services had been halted.

Becerra previously had served for more than a decade in Congress, representing parts of Los Angeles County. He had also served in the California state assembly after attending law school at Stanford.