Hugh Auchincloss was Anthony Fauci’s longtime deputy. Now he’s taking his job as House Republicans probe the pandemic.

Dr. Hugh Auchincloss, the acting director of the National Institute of Allergy and Infectious Diseases.National Institute of Allergy and Infectious Diseases

WASHINGTON — Dr. Anthony Fauci was the face of the fight against COVID-19, an omnipresent figure featured on T-shirts, bobbleheads, and yard signs. He was lionized by his fans as a scientific hero and villainized by his opponents as a denier of their freedoms.

But there are no tchotchkes with the likeness of the person who has replaced him at the helm of National Institute for Allergy and Infectious Diseases. In fact, finding more than one photo of Dr. Hugh Auchincloss on the Internet is a challenge.

Auchincloss, 73, a respected transplant surgeon and medical researcher, served for more than 16 years as Fauci’s low-key right-hand man at NIAID, a post he took after a long career at Massachusetts General Hospital. When Fauci retired at the end of last year, the director’s lab coat — and all the political heat that goes with it — went to Auchincloss as he became the agency’s acting head.

“He’s a highly accomplished immunologist,” Fauci told the Globe. “I fully expect that he will do an excellent job as the acting director.”

It’s unclear how long the search for a permanent replacement will take and whether Auchincloss is a candidate for the job, which does not require Senate approval. But for the time being, he’s leading the agency as the new House Republican majority launches a series of hearings on COVID-19. Although Fauci is expected to testify, Auchincloss also is likely to face questions.

Republicans are interested in Auchincloss because of a 2020 e-mail to him from Fauci. Some conservatives believe the message indicates that US health officials might have downplayed the possibility that the virus was artificially engineered in a Chinese laboratory through so-called gain of function research that was funded by the agency through a US nonprofit called EcoHealth Alliance.

On Feb. 2, three Republicans on the House Energy and Commerce Committee wrote to Dr. Lawrence Tabak, the acting director of the National Institutes of Health, requesting “all documents related to the origins of the COVID-19 pandemic” from Auchincloss, Fauci, and four other government doctors related to oversight of EcoHealth Alliance’s grant.

That letter followed one in December from the incoming chairs of the House Oversight and Judiciary committees asking Health and Human Services Secretary Xavier Becerra, who oversees NIH, for Auchincloss’s official calendars and phone records from late 2019 as well as an interview with him.

“He was absolutely involved and talked to Tony about it,” Lawrence O. Gostin, a public health expert at Georgetown Law School, said of the agency’s oversight of EcoHealth Alliance. “He’ll have to be able to defend that vigorously.”

But Gostin said Auchincloss will do it with a markedly different style than Fauci, who was accustomed to the spotlight as a high-profile adviser to presidents dating back to Ronald Reagan and became known for his willingness to go toe-to-toe with his loudest critic.

“He won’t have as strong and as confrontational a tone with Congress,” Gostin predicted of Auchincloss. “It’ll make it much more harder for Congress to attack him. He’s not been at the center of politics. He’s not taken visible public stances on controversial issues like lockdowns or school closures or masks.”

The father of Representative Jake Auchincloss of Newton, Hugh Auchincloss is the latest doctor with strong ties to Boston’s biomedical community to serve in a key Biden administration position, joining Dr. Rochelle Walensky, director of the Centers for Disease Control, and Dr. Ashish Jha, the White House COVID-19 response coordinator. Auchincloss is a 1976 Harvard Medical School graduate who spent 17 years running a laboratory at Massachusetts General Hospital focused on transplantation immunology before heading to NIAID in Bethesda, Md., in 2006.

“I got to know him over the years, both for his science management and his scientific credibility,” Fauci said of his decision to pick Auchincloss as his right-hand man. “He was the natural person for the job.”

Fauci had been the agency’s director since 1984, gaining renown during the fight against AIDS before he became the most prominent figure — and lightning rod — in the federal government’s response to the coronavirus pandemic. Auchincloss’s tenure with Fauci was spent out of the public eye, overseeing the agency’s research grants and projects.

Dr. Francis Delmonico worked with Auchincloss in the transplant division of Mass. General and praised him as “a brilliant scientist” who was particularly committed to juvenile diabetes research during his time there.

“He’s a charming man. If you had to be in a social evening conversation, Hugh is the person you’d want to be sitting next to,” Delmonico said. “He’s an outstanding scientist, someone with excellent clinical judgment, someone with all the capabilities to be the director of this institute.”

NIAID began the search for a permanent replacement for Fauci in November, saying it was seeking “exceptional candidates” to lead the agency, one of the largest under NIH, with an annual budget of $6.3 billion. Applications were due Jan. 17 and the search committee plans to forward the finalists to NIH leaders by late spring, NIH said in a statement. Becerra will make the final decision. Officials did not say whether Auchincloss had applied.

Fauci said he did not think Auchincloss was interested in the permanent position. But with a temporary director at NIH, it could take a while to pick a new head of NIAID.

Until then, Auchincloss is expected to hold the post, a departure from the low profile he’s maintained for years that has largely kept him out of the news.

Still, he hasn’t escaped the headlines altogether in recent years. In 2020, he helped fund a political action committee that backed his son’s first congressional campaign. Then last year, The Wall Street Journal reported that Hugh Auchincloss was one of several federal officials involved in the pandemic response who made stock trades in early 2020 before financial markets crashed.

Auchincloss sold nine mutual funds and one stock in January 2020 when the COVID outbreak had just begun. Auchincloss did not comment on the trades, and federal ethics officials told the Journal that he and others identified in the paper’s investigation did not violate any rules.

But it’s the 2020 e-mail he received from Fauci that could cause Auchincloss problems because it includes a reference to controversial gain of function research, a practice that involves manipulating viruses. The practice is risky because it can make a virus more transmissible and harmful. NIH halted funding for gain of function research from 2014-17 while it came up with new protocols for such projects.

In June 2021, BuzzFeed published more than 3,200 pages of Fauci’s e-mails it obtained from a Freedom of Information Act lawsuit. Just after midnight on Feb. 1, 2020, Fauci e-mailed Auchincloss saying, “It is essential that we speak this AM. Keep your cellphone on.” Fauci said he had a conference call later that morning and told Auchincloss to read a scientific paper he forwarded to him that had a title that included “SARS Gain of function.” SARS is part of the scientific name for the virus that causes COVID-19.

“You will have tasks today that must be done,” the e-mail concluded.

An inspector general’s report released last month found that NIH “did not effectively monitor” compliance by EcoHealth Alliance with some requirements regarding a study of bat coronaviruses by the Wuhan Institute of Virology in China it funded with federal money. That research has been central to people who contend the pandemic originated in the Wuhan lab and did not occur naturally, as federal officials have said is most likely. Those critics have pointed to Fauci’s e-mail to Auchincloss as evidence of a potential coverup of COVID-19′s origin.

Fauci told the Globe that the e-mail has been “completely misconstrued in a conspiratorial way.”

“There was nothing at all nefarious about those e-mails,” he said. “I was telling him to do his job, go and brief me about all the things that we’ve been doing so that when I get on the phone, I’ll know what we’re doing.”

Fauci oversaw the agency’s research but said he “delegated a considerable amount of that” responsibility to Auchincloss. Fauci is likely to be the focus of Republicans on the lab leak theory and could take some of the heat off of his former deputy, Gostin said.

“He’ll act like a lightning rod ... attract all of the energy toward him,” Gostin said, noting that will make it easier for Auchincloss if he also has to testify. “But I’m absolutely sure [Auchincloss] will defend the record of the agency and of Tony.”