WASHINGTON (AP) — President-elect Joe Biden has picked a former Food and Drug commissioner to lead vaccine science in his drive to put 100 million shots into the arms of Americans in his administration's first 100 days and stem the COVID-19 pandemic.

Dr. David Kessler, who will have the title of chief science officer of COVID response, headed the Food and Drug Administration in the 1990s under presidents of both political parties. He has been acting as a top pandemic adviser to Biden and his appointment was announced Friday by the presidential transition office.

Kessler will work out of the federal Department of Health and Human Services, assuming responsibility for the scientific side of Operation Warp Speed, an effort launched under the Trump administration to rapidly develop vaccines and treatments. The drive has already produced two highly effective vaccines, and more are on the way.

Nonetheless, the nation's vaccination campaign has gotten off to a slow start, and most of the vaccine being delivered to states by the federal government is not being used right away.

A person advising the Biden transition team said Kessler will take on the role now being carried out by Dr. Moncef Slaoui, a prominent vaccine scientist and innovator who has been serving as chief advisor to Operation Warp Speed. Several vaccine candidates in the pipeline are in final clinical trials, and one company is expected to soon apply for FDA emergency approval for its formulation. The person spoke on condition of anonymity to discuss internal deliberations.

Army Gen. Gustave Perna, who has been in charge of vaccine delivery under Operation Warp Speed, is expected to stay on.

Kessler, 69, will be able to start immediately as his post does not require Senate approval.

Kessler will coordinate vaccine review and approval, as well as the logistics of manufacturing millions more doses. Experts say the U.S. will need to vaccinate upwards of 250 million people to approach the goal of “herd immunity," where there is widespread resistance to virus allowing for a return to normal life. So far fewer than 12 million doses have been administered.

Kessler has been involved in a wide range of issues through his career, from the battle against HIV/AIDS, to tobacco regulation and improving the nutritional habits of Americans.

Appointed to head the FDA by President George H. W. Bush, he continued under President Bill Clinton.

Steering the agency from 1990 to 1997, Kessler earned nicknames like “Eliot Knessler” for his crusading efforts to enforce standards on everything from food labels to drug manufacturing.

His FDA legacy chiefly rests on a sweeping investigation into tobacco industry practices, which led the agency to label nicotine an addictive drug that companies purposely manipulated to hook smokers. Kessler drafted the U.S. government’s first-ever tobacco regulations, arguing that cigarettes were nicotine-delivery devices that deserved scrutiny akin to drugs or medical devices.

When Congress finally gave the FDA authority over key parts of the tobacco industry in 2009, the law borrowed heavily from Kessler’s initial ideas.

After leaving government, he worked as the dean of medical schools at Yale University and the University of California, San Francisco. In November, Biden named him to co-chair a panel of advisers on the COVID-19 response effort.