U.S. Assistant Health Secretary Dr. Rachel Levine was sworn in as a four-star officer during a uniformed event on Tuesday. She has become the first openly transgender person to attain the four-star admiral rank within the U.S. Public Health Service Commissioned Corps.

Before she was sworn in, the 63-year-old Biden appointee was already the highest-ranking transgender official in the country. She is also now the first female four-star admiral in the PHSCC. During her speech Tuesday, Levine described the occasions as a "historic" and "momentous" one. She also expressed her gratitude for being allowed to take the position.

"May this appointment today be the first of many more to come, as we create a diverse and more inclusive future," Levine said.

Levine previously worked as a professor of pediatrics and psychiatry at the Penn State College of Medicine before joining the U.S. Public Health Service. She is a graduate of Harvard College and Tulane University School of Medicine. Levine also worked as Pennsylvania's physician general and the state's secretary of health before her appointment.

Levine became the U.S. assistant secretary for health in March, following a 52-48 vote in the Senate. She was nominated by U.S. President Joe Biden in February. During her confirmation process, Levine outlined her work in handling the coronavirus pandemic as Pennsylvania's health secretary. She was also questioned about her work in tackling the widespread opioid crisis.

During much of the pandemic, Levine had led Pennsylvania's response to the health crisis. She also worked closely with FEMA and held daily press briefings to update the public on the state's COVID-19 situation.

The U.S. Public Health Service Commissioned Corps is comprised of roughly 6,000 uniformed officers. It is the federal uniformed service of the PHS and is one of the eight uniformed services of the country. The commissioned corps' main mandate is to respond to public health and safety crises such as pandemics and natural disasters.

Secretary of Health Xavier Becerra said Levine's appointment is a major step forward towards promoting equality. Becerra added that Levine is a "cherished and critical partner" in helping the PHS to achieve its goal of building a "healthier America."