Prince William, 38, was asked how his 99-year-old grandfather is by royal photographer Arthur Edwards, to which the Duke replied with a wink: "Yes, he's ok, they're keeping an eye on him."
WATCH: Prince William shares health update about Prince Philip as he visits vaccination centre
Prince Philip spent a sixth night at King Edward VII’s hospital in London after being admitted last Tuesday as a "precautionary measure" after feeling unwell. HELLO! understands that the Duke walked in unaided and it was not an emergency admission.
Charles visited his father in hospital on Saturday
William's comments came as he visited a vaccination centre at the King's Lynn Corn Exchange in Norfolk on Monday to pay tribute to the incredible efforts and dedication of the staff involved in the Covid-19 vaccine rollout.
The Duke spoke with NHS staff and volunteers about their experiences, as well as meeting with a number of people receiving their vaccine that day.
William, who contracted the virus himself last April, asked vaccinator Debbie Rudd, 50, whether the patients were nervous, adding: "I'd be at the front of the queue if I could, just to prove that it's OK, but I have to wait my turn."
He later told staff: "Honestly, you guys have overcome every challenge that's been thrown at you. Brilliant work."
Cambridgeshire Community Services NHS Trust delivers the four large-scale vaccination centres across Cambridgeshire, Peterborough, Norfolk and Waveney, alongside a number of GP and pharmacy-led sites. The vaccination centre at the Corn Exchange King's Lynn opened on 1 February and has delivered thousands of vaccines every week since.
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