Prince Philipspent the third night in a London hospital after beingadmitted on Tuesdayfor what Buckingham Palace described as “a precautionary measure” — and he’ll remain in the hospital for “observation and rest” into next week.

Queen Elizabeth’s 99-year-old husband was taken to the King Edward VII Hospital on Tuesday evening on the advice of his doctor after “feeling unwell,” Buckingham Palace said in a statement at the time. The royal was expected to remain in the hospital for a few days.

On Friday, a royal source told PEOPLE that Philip is now expected to remain in the hospital “into next week.”

Prince Philip.Royal Family/Twitter

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Palace sources stressed after Tuesday’s admission to the hospital that this was not an emergency admission and that Philip walked into the hospital unaided.

Queen Elizabeth and Prince Philip.Steve Parsons/Press Association via Getty

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The illness is not COVID-19-related. Both the Queen, 94, andPrince Philipreceived the first dose of the coronavirus vaccinein early January.

Prince Philip.Tim Graham Photo Library via Getty

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He abruptly canceled his appearance at the traditional Maundy church service that he was scheduled to attend with the monarch in March 2018. Philip also skipped Easter Sunday services that year ahead of the announcement that he underwent hip replacement surgery.

The royal had acar accidentin January 2019 that resulted in him voluntarilygiving up his license.

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AmidPrince Philip’s hospitalization,Queen Elizabethhas remained at Windsor Castle, where the couple has spent much of the year in isolation during the coronavirus pandemic.

In early November, Philip and the Queenreturned to Windsor Castle togetherafter spending a weekend at Sandringham. They hadspent a few weeks apart in Octoberwhen Philip stayed at Wood Farm on her estate in Norfolk while the Queen went to Windsor Castle.

source: people.com