A White House spokesman confirmed the positive cases, adding that neither the White House official nor Pelosi's aide were showing severe symptoms because both had previously been vaccinated.
"We know that there will be breakthrough cases, but as this instance shows, cases in vaccinated individuals are typically mild," the spokesman told Axios.
The Pelosi staffer and the White House official, who each tested positive, both attended a rooftop reception at the Hotel Eaton last Wednesday evening. Previously, the Pelosi staffer met with the Texas lawmakers and ushered them around the Capitol.
Neither individual has had recent direct contact with either President Joe Biden or Speaker Pelosi.
"Yesterday, a fully vaccinated White House official tested positive for COVID-19 off campus," the White House spokesperson said in a statement.
"In accordance with our rigorous COVID-19 protocols, the official remains off campus as they wait for a confirmatory PCR test. The White House Medical Unit has conducted contact tracing interviews and determined no close contacts among White House principals and staff. The individual has mild symptoms."
The spokesperson added, "The White House is prepared for breakthrough cases with regular testing. This is another reminder of the efficacy of the COVID-19 vaccines against severe illness or hospitalization. We wish our colleague a speedy recovery."
Pelosi's deputy chief of staff, Drew Hammill, said, "Yesterday, a fully-vaccinated senior spokesperson in the Speaker's press office tested positive for COVID after contact with members of the Texas state legislature last week."
"The entire press office is working remotely today with the exception of individuals who have had no exposure to the individual or have had a recent negative test. Our office will continue to follow the guidance of the Office of Attending Physician closely," he added.
Coronavirus cases in the U.S. have begun to rise due to the Delta variant, a strain of the coronavirus from India that is more contagious than other variants but not more severe. Because the Delta variant is more transmissible, even vaccinated people may become infected but their symptoms will only be mild and the risk of hospitalization or death from COVID-19 is dramatically reduced by vaccination.
According to the Centers for Disease Control and Prevention, vaccine breakthrough cases are expected as no vaccine is 100% effective at preventing illness in vaccinated people.
In the U.S., more than 159 million people have been fully vaccinated against COVID-19. CDC data indicates that 5,429 patients who were vaccinated experienced a breakthrough infection and were hospitalized or died. The CDC notes the number of breakthrough infections reported is likely undercounted, as it relies on passive and voluntary reporting.
"Vaccine breakthrough cases occur in only a small percentage of vaccinated people," the CDC says. "To date, no unexpected patterns have been identified in the case demographics or vaccine characteristics among people with reported vaccine breakthrough infections."
The Texas Democrats who traveled to D.C. to lobby for federal legislation that would undo Republican election security laws are currently in quarantine, continuing their efforts over Zoom. State Rep. Rafael Anchia (D), told the Dallas Morning News the lawmakers have been "observing all CDC guidelines."
"We're grateful that 100% of us were vaccinated in advance," he said. "This delta variant is no joke."