When President Joe Biden is sworn into office, he will assume stewardship of the nation's COVID-19 response at a pivotal moment: America is climbing towards 400,000 deaths, a new variant of the virus has arrived from the U.K., and vaccine rollout has been slower than projected.

Biden's pick to lead the Centers for Disease Control and Prevention, Dr. Rochelle Walensky, has vowed to be a transparent public face for an agency mired by political meddling during the COVID-19 response. Walensky, who's led the Infectious Diseases Division at Massachusetts General Hospital for the past three years, is a renowned HIV researcher known for her analysis of cost-effectiveness of HIV care and increased screening.

In a recent New York Times column, Walensky wrote that the CDC’s reputation has been “tarnished.” She vowed an immediate and comprehensive review of the agency to ensure all guidance is “evidence-based and free of politics.”

Walensky, 51, has never led a government agency before. She will have to boost morale at the CDC, after months of of being undermined by the Trump administration.

Dr. Kenneth Freedberg, a physician at MGH who’s worked with Walensky for the past 20 years, said he was shocked, but not surprised when he found out about Walensky's new job; only two other people have led MGH's Infectious Diseases Division in the past 70 years, and he expected her to stick around a little bit longer.

But, Freedberg said Walensky's career has prepared her to take on this role, especially in such a fraught moment.

“Someone who can bring science and understanding and people skills to this challenging time we’re in, and be able to talk to people about what we need to do, I think she’s perfectly suited," said Freedberg.

Walensky, who was born in Peabody, got her medical degree from Johns Hopkins University School of Medicine, and returned to the Boston area for a joint fellowship at Mass General and Brigham and Womens Hospitals in the late 1990s.

At the time, the HIV/AIDS epidemic was tearing through communities, but the policies and treatments were just starting to change for the better. Her interest in HIV research compelled her to stay in Boston, where she has been a professor of medicine at Harvard Medical School, and a physician at both Mass General and Brigham and Womens Hospitals.

Her work has radically expanded access to treatment and helped end stigma around HIV, Mass General colleague Dr. Robbie Goldstein said.

"The work that Rochelle has done over the past 20 years is to revolutionize the world of HIV and the care that we provide, but it’s work that has set the framework for advancements in all infectious diseases,” he said.

Since March, Walensky had also served on Gov. Charlie Baker's COVID-19 Advisory Board, advocating for equitable access to the vaccine as the state began distribution. Goldstein said he expects Walensky will bring that focus on equity to the CDC.

"She’s always thinking about who’s most vulnerable and how is this plan going to make sure that those most vulnerable will receive what they need," he said.

Jennifer Kates, director of Global Health and HIV policy at the Kaiser Family Foundation, said the parallels between COVID-19 and HIV are significant, and that Walensky’s experience in both realms have positioned her well for this moment.

“A lot of us see incredible parallel — a new, emerging virus that has scared people, the need to identify the virus, no treatments at the beginning, testing has been fraught — all of these things were challenging in early days of HIV and still exist," she said.

Kates said Walensky will seek to address the systemic issues that lead to inequities in health, and steer the CDC towards again being the agency relied on by doctors and the general public alike, for national guidelines on public health.

“We’ve seen that’s been stymied over the last few years, especially the last year, so I think she will focus on how the nation’s public health agency can be a stronger voice, for individuals, for schools, for state and local government, for employers," said Kates.

As the nation lags behind its own projections for vaccine distribution, and new variants of the virus are beginning to be logged in states, the Biden administration has vowed to be more aggressive in its response to the pandemic, through things like mask mandates and mass vaccination sites.

While Trump's CDC Director Robert Redfield hadn't been much of a presence over the past few months, Walensky has pledged to be a very public face of the nation’s top public health agency, by conveying the science first and foremost.