Queen Elizabeth is being monitored for COVID-19 after her son, Prince Charles, tested positive for the virus on Thursday, according to Buckingham Palace.

A royal source told ABC News the 95-year-old queen and Prince Charles, 73, met recently. The queen is not displaying any symptoms of COVID-19 at this time, according to the source.

Prince Charles, who is now self-isolating, attended an event Tuesday at Windsor Castle, where the queen recently returned after spending time at Sandringham, her Norfolk estate.

This is the second time Prince Charles has tested positive for COVID-19, with his first diagnosis coming in March 2020, before he was vaccinated.

Buckingham Palace has not said if Queen Elizabeth has been tested for COVID-19.

“With the queen, they’re balancing the situation,” said ABC News royal contributor Victoria Murphy. “She is head of state and there is a sense that the public does need and want to know, but at the same time, she’s a very elderly lady who is entitled to a certain amount of medical privacy.”

Queen Elizabeth, Britain’s longest-reigning monarch, was last seen publicly on Saturday at an event in Sandringham to mark her 70 years on the throne.

The queen met with representatives from local community groups in the ballroom at Sandringham House to celebrate the start of the Platinum Jubilee.

It was the queen’s first public, in-person event since October, when she was hospitalized for one night for what the palace described as “preliminary investigations.”

After being advised by her doctors to rest, Queen Elizabeth took on a more modified schedule. In November, she missed the annual Remembrance Sunday Service for the first time in her reign due to a sprained back.

The queen had already modified her schedule throughout the coronavirus pandemic, holding virtual audiences and participating in video calls instead of public events.

When her husband, Prince Philip, died at age 99 last April, the queen sat alone during the funeral service in St. George’s Chapel, following pandemic restrictions.

Both Queen Elizabeth and her late husband received their first COVID-19 vaccination shots in January 2021, Buckingham Palace confirmed at the time.

Prince Charles and his wife, Camilla, the Duchess of Cornwall, confirmed in December that they had both received their booster shoots of the vaccine, according to the BBC.