Kate Middleton is self-isolating.

Kate, 39, pulled out of events alongside her husband Prince William on Monday because she has come into contact with someone who tested positive for COVID-19, the palace said. The mom of three is not experiencing any symptoms.

Her office at Kensington Palace confirmed the news just before she and William were set to arrive at St. Paul's Cathedral in London for a service of thanksgiving for the U.K.'s public health service, the NHS.

A spokesperson for the palace said in a statement, "Last week, The Duchess of Cambridge came into contact with someone who has subsequently tested positive for COVID-19. Her Royal Highness is not experiencing any symptoms, but is following all relevant government guidelines and is self-isolating at home."

Kate had previously been scheduled to attend the service at St. Paul's Cathedral and to join William later this afternoon hosting a tea party in the gardens at Buckingham Palace.

Kate publicly shared that she received her first vaccination on May 28. She reportedly discovered she has been exposed to the virus on Friday. She spent part of Friday at the Wimbledon tennis championships.

British Government guidelines mean she has to isolate at home for 10 days following exposure.

William arrived at the NHS service at the magnificent St. Paul's Cathedral at around 11a.m. local time on Monday. Guests included leading figures in the NHS' pandemic response and several hundred members of frontline staff, patients and others involved in the NHS response to Covid-19 were among those attending the service.

Among the congregation were NHS Chief Sir Simon Stevens, Matron May Parsons, who administered the first ever COVID-19 shot outside of clinical trials, Sam Foster, the nurse who gave the first Oxford Astra Zeneca vaccine, members of staff who treated the first COVID-19 patients in England and a number of patients who have been treated for the virus.