The Prince of Wales and the Duchess of Cornwall have both been fully vaccinated and have received their respective booster shots.
After Camilla returned a negative result following Charles' positive one, she continued to carry out several royal engagements, as allowed under government guidelines.
It was revealed that Prince Charles had contracted COVID for the second time just four days ago.
"This morning The Prince of Wales has tested positive for COVID-19 and is now self-isolating," Clarence House said in a statement on Twitter, adding that they were "deeply disappointed" that he would not be able to attend the upcoming royal engagement in Winchester.
The news came just days after Charles had reportedly met with Queen Elizabeth at Windsor Castle, though she is currently not displaying any symptoms and continues to be monitored.
Back in March 2020, the Prince of Wales tested positive for COVID-19 and detailed how the mild case saw him temporarily lose his sense of taste and smell.
WATCH: Prince William congratulates Oxford University on Covid-19 vaccine breakthrough (Article continues after video)
In early 2021 the Queen confirmed she had received her first COVID vaccine dose while encouraging others to also get the jab during a video call with U.K. health officials.
"Once you've had the vaccine you have a feeling of, you know, you're protected, which is I think very important," Her Majesty said, as per Sky News.
"As far as I could make out it was quite harmless. It was very quick, and I've had lots of letters from people who have been very surprised by how easy it was to get the vaccine. And the jab—it didn't hurt at all."