WASHINGTON — President Biden was feeling fine on a quick trip to Massachusetts Wednesday, delivering a nearly 20-minute speech in scorching heat outside a shuttered power plant in Somerset then cheerfully working the crowd in his aviator sunglasses before flying back to the nation’s capital.
But some fatigue set in later that night, and after sleeping restlessly, he woke up with a runny nose and a dry cough, White House officials said. A regularly scheduled test Thursday morning delivered the news that has seemed inevitable despite the administration’s efforts to protect the oldest US president in history: Biden has COVID-19.
“We knew this was going to happen,” White House press secretary Karine Jean-Pierre told reporters.
But unlike former president Donald Trump’s bout with the disease before vaccines were available in 2020, Biden’s diagnosis triggered much less drama and concern. Biden is fully vaccinated and double boosted, was experiencing mild symptoms, and, after he started immediately on Paxlovid, an antiviral drug designed to reduce the severity of the disease, White House doctors and outside physicians said his prognosis was good despite his age of 79.
“Most elderly vaccinated people do really well with COVID,” said Dr. Shira I. Doron, hospital epidemiologist at Tufts Medical Center. “The chance of Biden doing really well is really, really high.”
None of the Massachusetts politicians who traveled with Biden Wednesday or appeared with him at the Somerset event had tested positive as of Thursday. And the White House sought to downplay the impact of Biden’s illness, which comes as the BA.5 variant has caused a sharp jump in infections — though notably not deaths — nationwide. Although his travel was canceled for at least five days, Biden tweeted a photo of himself working at his desk and later a video of him outside on a balcony, shot by a socially distanced videographer who the White House said was wearing an N95 mask.
“I’m doing well, getting a lot of work done, going to continue to get it done,” an upbeat Biden said in the video. “And in the meantime, thanks for your concern and keep the faith. It’s going to be OK.”
White House officials also used the moment to stress the importance of Americans getting vaccinated and testing if they believe they have symptoms, and if positive, immediately starting on antiviral medications that can improve their chances for a quick recovery.
“Because the president is fully vaccinated, double boosted, his risk of serious illness is dramatically lower,” said Dr. Ashish Jha, the White House COVID-19 response coordinator. “And it’s a reminder of the reason that we all worked so hard to make sure that every American has the same level of protection as the president has.”
Biden’s positive test came after he was joined on Air Force One for his trip to Massachusetts Wednesday by four members of the state’s congressional delegation, including Senators Elizabeth Warren, 74, and Ed Markey, 76. According to the White House, he then participated in a photo line at the event highlighting the need to combat climate change with several Massachusetts state officials.
All passengers on Air Force One were required to produce negative COVID tests before boarding as part of White House protocol. As the news of Biden’s infection hit Washington, some lawmakers and other officials who spent time with him Wednesday were so far testing negative. They included Warren, Markey, and Senator Sheldon Whitehouse, 66, a Rhode Island Democrat, as well as Representatives Bill Keating, 69, of Bourne, and Jake Auchincloss, 34, of Newton, who had posted photos on Twitter of him and Biden in close contact on Air Force One.
Two top state Democrats who attended the Somerset event, Senate President Karen E. Spilka, 69, of Ashland, and House Speaker Ronald Mariano, 75, of Quincy, also tested negative on Thursday, according to their spokespeople. Former Massachusetts senator John Kerry, 78, who is now serving as Biden’s special presidential envoy for climate, attended the Somerset event as well and has tested negative, according to a spokesperson.
A fresh COVID outbreak among Democratic senators would be ill-timed for the caucus, given their hair-thin majority and shrinking number of legislative days left before the August recess begins.
Biden had tested negative on Tuesday, his last test before Thursday morning, Jean-Pierre said. Vice President Kamala Harris, 57, was last with Biden on Tuesday and tested negative on Thursday, according to a White House official. She continued with a planned trip to North Carolina but will wear a mask on the advice of the White House medical team, the official said.
First lady Jill Biden, 71, also did not cancel her planned trip to Detroit. She told reporters she tested negative Thursday morning and was wearing a mask in accordance with CDC guidelines.
The relative calm was a striking difference to the reaction to Trump’s positive COVID test in October 2020, before vaccines were available and when treatment options were limited. When his blood oxygen levels fell dangerously low, Trump, then 74, was rushed by helicopter to Walter Reed National Military Center, where he was hospitalized for three days.
In contrast, Biden’s blood oxygen level was normal Thursday, Jha said, and the president was set to isolate in the White House residence under close monitoring. Jean-Pierre promised daily updates on his condition.
“We worry most about immunocompromised and older patients,” said Dr. Camille Kotton, an infectious disease specialist at Massachusetts General Hospital. “With respect to COVID-19, the majority of people do quite well with outpatient treatment. I would be cautiously optimistic that with good treatment he would do quite well and hopefully won’t be sick too long.”
White House officials said they did not know when or how Biden caught the virus. But with the new variant spreading rapidly and Biden out in the public, they saw this outcome as inevitable. In recent months, many top officials in his administration, including Harris and multiple Cabinet secretaries, have tested positive for COVID, as have dozens of members of Congress.
“Let people know that none of us is immune from it, including the president of the United States, and we really have to be careful,” said House Speaker Nancy Pelosi. The 82-year-old California Democrat contracted COVID this spring and said Thursday she had a “light” case of the disease.
“Let’s hope that it would encourage people to be tested, to have the vaccines, the boosters, and the rest,” she said.
Biden was extremely cautious about COVID during the 2020 presidential campaign and during his first year in the White House, frequently wearing a mask and keeping social distance. But as virus case counts fell this year, the White House dropped its mask mandate for vaccinated people and Biden has spent more time unmasked and in the public.
“The president wants to get out there and meet the American people and engage, and we always said this was a possibility,” Jha told reporters, adding that the White House protocols had helped stave off an infection until now. “The good news is his immune system is very well protected given the four vaccine shots he’s gotten. He’s getting treatment. He has mild symptoms. He’s feeling fine — his words.”
Travis Andersen of the Globe staff contributed to this report.
Correction: Because of incorrect information provided to the reporter, a previous version of this story incorrectly included the presence of a local Massachusetts official who was not at the photo line Wednesday in Somerset, Mass., with President Biden. Also, because of reporting error, a previous version incorrectly listed a passenger on Air Force One and the age of Representative Bill Keating. The Globe regrets the errors.