A White House official and a staff member for House Speaker Nancy Pelosi (D-Calif.) have both tested positive for COVID-19 after attending the same reception last week, officials confirmed to Axios.

Why it matters: While both individuals are vaccinated and mildly symptomatic, they illustrate how Americans inoculated against the coronavirus can still contract and, potentially, unknowingly transmit the virus at the highest levels of the nation's government.

• "We know that there will be breakthrough cases, but as this instance shows, cases in vaccinated individuals are typically mild," a White House official told Axios.

Driving the news: The Pelosi staffer helped usher a delegation of Democratic Texas lawmakers around the Capitol last week. Six of those lawmakers, who flew to Washington to block the Texas legislature from changing the state's voting laws, have since tested positive.

• Both that staffer and the White House official were at the same rooftop reception at the Hotel Eaton last Wednesday night.
• The White House official has not had any recent direct contact with President Biden. The Pelosi aide did not have any contact with the speaker since that person's exposure.

What they are saying: "Yesterday, a fully vaccinated White House official tested positive for COVID-19 off campus," a White House official told Axios 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 official 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."

Drew Hammill, deputy chief of staff to Pelosi, told Axios in a statement: "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."

The big picture: COVID-19 cases are on the rise across the country, with health officials becoming increasingly worried about the Delta variant. It's significantly more infectious than the original strain, and poses an acute threat to the unvaccinated.

• Concern about the Delta variant of COVID-19 is causing some places to consider reinstating mask recommendations. A legislative aide also cited the variant in telling Axios' Alayna Treene on Monday that public tours of the Capitol would not resume in the near future.
• Most Americans who still aren't vaccinated say nothing — not their own doctor, a celebrity's endorsement or even paid time off — is likely to make them get the shot, according to the latest installment of the Axios/Ipsos Coronavirus Index.
• On Monday, Rep. Vern Buchanan, (R-Fla.) announced he had tested positive for coronavirus after being fully vaccinated, becoming the first known positive case in Congress this summer.